3 different way Tree Traversal

=========================================================================
Node class for tree

class Node{
    int data;
    Node left;
    Node right;
}

=========================================================================
Case 1: pre-order 

Recursive

public static void preOrderRecursive(Node root){
    if(root == null)
        return;
		
    System.out.print(root.data + " ");		
    preOrderRecursive(root.left);
    preOrderRecursive(root.right);
}

NON-Recursive

public static void preOrderIterative(Node root){
    if(root == null)
        return;
		
    Stack<Node> unvisited = new Stack<Node>();
    unvisited.push(root);
	
    while(!unvisited.isEmpty()){
        Node node = unvisited.pop();
			
        System.out.print(node.data + " ");
        if(node.right != null)
            unvisited.push(node.right);
        if(node.left != null)
            unvisited.push(node.left);
    }	
}

=========================================================================
Case 2: in-order 

Recursive

public static void inOrderRecursive(Node root){
    if(root == null)
        return;	
	
    inOrderRecursive(root.left);
    System.out.print(root.data + " ");
    inOrderRecursive(root.right);
}

NON-Recursive

public static void inOrderIterative(Node root){
    if(root == null)
        return;
		
    Stack<Node> unvisited = new Stack<Node>();
		
    while(!unvisited.isEmpty() || root != null){
        if(root != null){
            unvisited.push(root);
            root = root.left;
        }else{
            root = unvisited.pop();
            System.out.print(root.data + " ");
            root = root.right;
        }
    }
}

========================================================================= 
Case 3: post-order 

Recursive

public static void postOrderRecursive(Node root){
    if(root == null)
        return;
		
    postOrderRecursive(root.left);
    postOrderRecursive(root.right);
    System.out.print(root.data + " ");		
}

NON-Recursive

public static void postOrderIterative(Node root){
    if(root == null)
        return;
		
    Stack<Node> finalStack = new Stack<Node>();
    Stack<Node> tempStack = new Stack<Node>();
	
    tempStack.push(root);
    while(!tempStack.isEmpty()){
        Node node = tempStack.pop();
        finalStack.push(node);
        if(node.left != null)
            tempStack.push(node.left);
				
        if(node.right != null)
            tempStack.push(node.right);
    }
	
    while(!finalStack.isEmpty()){
        Node node = finalStack.pop();
        System.out.print(node.data + " ");	
    }
}

Find a missing integer in an array of number

Find a missing integer in an array of number

Case 1: Sorted
Use two pointers to store previous and current value, and difference between two number should equal to 1.

public static int findMissing_Sorted(int[] input){
    if(input.length == 0)
        return 0;

    int prev = input[0];
    for(int i = 1 ; i < input.length ; i++){
        int curr = input[i];
        if((curr - prev) != 1)
            return (prev + 1);
        else
            prev = curr;
    }
    return 0;
}

Case 2: Unsorted
Get the sum of 1 to N, use formula sum = (N+1)*(N)/2
Minus the element in the array, and the remaining value is the missing number.

public static int findMissing_Unsorted(int[] input){
    if(input.length == 0)
        return 0;
   
    int N = 10;
    int max = (N + 1) * N / 2;
  
    for(int i = 0 ; i < input.length ; i++)
        max -= input[i];
   
    return max;
}

How to use *args and **kwargs in Python

from
http://www.saltycrane.com/blog/2008/01/how-to-use-args-and-kwargs-in-python/

http://docs.python.org/tutorial/controlflow.html#keyword-arguments

def test_var_args(farg, *args):
    print "formal arg:",farg
    for arg in args:
        print  "another arg:",arg
  


def test_var_kwargs(farg, **kwargs):
    print "formal arg:",farg
    for key in kwargs:
        print "another keyword arg: %s: %s" % (key, kwargs[key])

test_var_args(1, "two", 3, "four")
print '-'*40
test_var_kwargs(farg = 1, myarg2 = "two", myarg3 = 3, myarg4 = "four")

def test_var_args_call(arg1, arg2, arg3):
    print "arg1:", arg1
    print "arg2:", arg2
    print "arg3:", arg3

args = ("two", 3)
test_var_args_call(1, *args)

def test_var_args_call(arg1, arg2, arg3):
    print "arg1:", arg1
    print "arg2:", arg2
    print "arg3:", arg3

kwargs = {"arg3": 3, "arg2": "two"}
test_var_args_call(1, **kwargs)

Codeforce - 158A - Next Round

n, k = map(int, raw_input().strip().split() )
seq = map(int, raw_input().strip().split() )

score = seq[k - 1]

if score == 0:
    counter = 0
    for i in range(0, k):
        if seq[i] > score:
            counter += 1
    print counter
 
else:
    counter = k
    for i in range(k, n):
        if seq[i] >= score:
            counter += 1
        else:
            break
    print counter

ACM105 -- The Skyline Problem

#include <iostream>

using namespace std;

int main()
{
    int L,H,R;
    int counter = 0;
    int temp_pre,temp_curr;
    int min = 20000,max = 0;
    int building[10001] = {0};


    while(cin>>L>>H>>R)
    {
        if(min>L)
        min = L;

        if(max<R)
        max = R;

        for(int i = L ; i < R ; i++)
        {
            if(building[i] < H)
            building[i] = H;
        }
        counter++;
    }



    bool check = true;
    temp_pre = building[min];
    cout<<min<<" "<<temp_pre<<" ";

    for(int j = min+1 ; j <= max ; j++)
    {
        temp_curr = building[j];
        if(check) //check == true
        {
            if(temp_curr == 0)
            {
                check = false;
                cout<<j<<" "<<temp_curr;
            }else
            {
                if(temp_curr != temp_pre)
                {
                    cout<<j<<" "<<temp_curr<<" ";
                    temp_pre = temp_curr;
                }
            }
        }
        else
        {
            if(temp_curr == 0)
            {
                //do nothing
            }else
            {
                check = true;
                temp_pre = temp_curr;
                cout<<" "<<j<<" "<<temp_curr<<" ";
            }
        }
    }

    cout<<endl;
    return 0;
}

Codeforces -- 1A -- Theater Square

#include <iostream>
#include <math.h>

using namespace std;

int main(int argc, char* argv[]){
    long double n,m,a;

    cin>>n>>m>>a;

    long long res = (long long)(ceil(n/a) * ceil(m/a));

    cout<<res;
 return 0;
}

ACM 10035 -- Primary Arithmetic

#include <iostream>

using namespace std;


int main(int argc, char* argv[]){
    unsigned long long n1;
    unsigned long long n2;
    int carry = 0;
    int sum = 0;
    int count = 0;

    while(cin >> n1 >> n2) {
        if(n1 == 0 & n2 == 0)
            break;

        carry = 0;
        count = 0;
        sum = 0;

        while ((n1 > 0) || (n2 > 0)) {

            sum = carry + (n1 % 10) + (n2 % 10);

            if (sum >= 10) {
                count++;
            }

            carry = sum / 10;

            n1 /= 10;
            n2 /= 10;
        }

        if (count == 0) {
            cout << "No carry operation." << endl;
        } else if (count == 1) {
            cout << "1 carry operation." << endl;
        } else {
            cout << count << " carry operations." << endl;
        }
    }
 return 0;
}

ACM 494 -- Kindergarten Counting Game

#include <stdio.h>
#include <ctype.h>


int main()
{
    char temp;
    int counter = 0;
    int isWord = 0;
    while((temp = getchar()) != EOF){
        if(temp == '\n'){
            printf("%d\n", counter);
            counter = 0;
            isWord = 0;
        }else{
            if((temp >= 65 && temp <= 90)||(temp >= 97 && temp <= 122)){
                if(isWord == 0){
                    isWord = 1;
                    counter++;
                }
            }else{
                if(isWord == 1){
                    isWord = 0;
                }
            }
        }
    }
    return 0;
}

ACM 10038 -- Jolly Jumpers

#include <stdio.h>
#include <math.h>


int main(int argc, char* argv[])
{
    int counter;
    int num[3000];
    int flag[3000];

    while( scanf("%d", &counter) == 1 ){
        int i;
 for(i = 0 ; i < counter ; i++){
            scanf("%d", &num[i]);
            flag[i] = 0;
        }

        int res = 0;
        for(i = 1 ; i < counter ; i++){
            int diff;
            if(num[i] > num[i-1]){
                diff = num[i] - num[i-1];
            }else{
                diff = num[i-1] - num[i];
            }

            if(0 < diff && diff < counter){
                if(flag[diff] == 0){
                    flag[diff] = 1;
                }else{
                    res = 1;
                    break;
                }
            }else{
                res = 1;
                break;
            }

        }

        if( res == 1 ){
            printf("Not jolly\n");
        }
        else{
            printf("Jolly\n");
        }
    }
 return 0;
}

ACM 458 -- The Decoder

#include <stdio.h>
#include <ctype.h>


int main()
{
    char temp;
    while((temp=getchar())!=EOF)
    {
        (temp == '\n') ? putchar(temp) : putchar(temp-7);
    }
    return 0;
}

ACM 272 -- TEX Quotes

#include <stdio.h>
#include <ctype.h>


int main()
{
    char temp;
    int pair = 0;
    while((temp=getchar())!=EOF){
        if(temp == '"'){
            if(pair == 0){
                pair++;
                printf("``");
            }else{
                pair = 0;
                printf("''");
            }
        }else{
            putchar(temp);
        }
    }
    return 0;
}

ACM 10071 -- Back to High School Physics

#include<stdio.h>
#include<stdlib.h>

int main()
{
    int v, t;
    while (scanf("%d %d",&v, &t)!= EOF){
        printf("%d\n", 2*v*t);
    }
    return 0;
}

ACM 10055 -- Hashmat the Brave Warrior

#include <stdio.h>


int main()
{
    long long int hash, oppen;
    while (scanf("%lld %lld",&hash, &oppen)!= EOF){
        if(hash > oppen)
            printf("%lld\n", (hash - oppen));
        else
            printf("%lld\n", (oppen - hash));
    }
    return 0;
}

ACM 10110 -- Light, more light

#include <iostream>
#include <math.h>
#include <sstream>
#include <stdio.h>
#include <cstdio>

using namespace std;

bool willLight(double num){
    long long int test = (int) sqrt(num) ;

    if(test*test == num)
        return true;


    return false;
}


int main()
{
    double input;

    while(scanf("%lf", &input)){
        if(input == 0.0)
            break;

        if( willLight(input) )
            cout<<"yes"<<endl;
        else
            cout<<"no"<<endl;
    }

    return 0;
}

ACM 492 -- Pig-Latin

#include <stdio.h>
#include <ctype.h>
int test(char ch);

int main()
{
    int i;
    char ch;
    char root;
    int s;

    while(1){
        i = 0;
        while(1){
            ch = getchar();
            if(ch == EOF)
                return 0;
            if(isalpha(ch)){
                if(!i){
                    s = test(ch);

                    if(s)
                        printf("%c", ch);
                    else
                        root = ch;
                    i++;
    }else{
                    printf("%c", ch);
                }
            }else{
                if(!i){
                    printf("%c", ch);
                    break;
                }
                if(s){
                    printf("ay%c", ch);
                }else{
                    printf("%cay%c", root, ch);
                }
                break;
            }
        }
    }
    return 0;
}

int test(char ch){
 if(ch == 'A' || ch == 'a')
  return 1;
 if(ch == 'E' || ch == 'e')
  return 1;
 if(ch == 'I' || ch == 'i')
  return 1;
 if(ch == 'O' || ch == 'o')
  return 1;
 if(ch == 'U' || ch == 'u')
  return 1;

 return 0;
}

Django -- redirect to outside link

in views.py

out_url = "http://www.google.com"
return render_to_response('short/redirect.html', {'out_url':out_url})

in short/redirect.html

<meta http-equiv="refresh" content="0; URL={{ out_url }}">

Django -- upload file

上傳資料，參考
http://oranlooney.com/django-file-uploads/
http://www.nitinh.com/2009/02/django-example-filefield-and-imagefield/
http://gibuloto.com/blog/models-dot-imagefield/ 

(1)設定上傳用的資料夾
Django 1.4 裡面有提供 MEDIA_URL 和 MEDIA_ROOT
這兩個部份的設定主要是讓使用者上傳資料和顯示

這邊就不從開新的app開始說，直接從settings.py和models.py設定開始

首先是settings.py的設定

cd //var/www/mutarock/mutarock
vim settings.py

MEDIA_ROOT = os.path.join(os.path.dirname(__file__), '..', 'multimedia').replace('\\','/')
MEDIA_URL = '/multimedia/'

設定完之後移到上一層去

cd ..
mkdir multimedia

接下來是apps裡面models.py的設定

class Picture(models.Model):
    image = models.ImageField(upload_to='pic')

上面的models開了一個欄位，讓使用者上傳圖片，在django裡面，系統不會真的把東西儲存在資料庫裡面
而是儲存資料在系統裡面的位置

MEDIA_ROOT 和 upload_to 的設定，有以下的關係

MEDIA_ROOT = ‘/home/myname/files/
upload_to=’videos’
file: abc.flv
results in: /home/myname/files/videos/abc.flv

MEDIA_ROOT = '/home/myname/files/'
upload_to='/videos'
and file : abc.flv
result will be saved in : '/videos/abc.flv' (i.e., root directory of filesystem)

upload_to也可以加進去上傳的日期和時間
upload_to='videos/%Y/%m/%d'
如果上傳時間是2012 Jun 12
檔案就會儲存到 /home/myname/files/videos/2012/06/12

(2)設定form.py
form的部分可以直接建立在html裡面，網路上的參考文章則是順便教了如何用django實做form
連到自己的apps裡面新增一個form.py

vim form.py

輸入下面的code

from django import forms
from PIL import Image
class PictureUploadForm(forms.Form):
    image = forms.ImageField()
    

    def clean_image(self):
        ' reject large images.'
        max_size = 10**7
        if len(self.cleaned_data['image'].read()) > max_size:
            raise forms.ValidationError('Image must be less then %d bytes.' % max_size)
        else:
            return self.cleaned_data['image']

上面的code會有一個可以欄位，讓使用者決定要上傳什麼圖檔
其中也自訂一個function，檢查上傳的檔案是否超過我們自定的大小

(3)設定views.py

import uuid #use for data name
from apps.picture.form import PictureUploadForm  #import your form

def picture_upload(request):

    picture = Picture()
    if request.method != 'POST':
        form = PictureUploadForm()
    else:
        form = PictureUploadForm(request.POST, request.FILES)
        if form.is_valid():

            # an UploadedFile object
            uploadedImage = form.cleaned_data['image']
            file_name = uuid.uuid4().hex
            file_extension = os.path.splitext(uploadedImage.name)[-1]
            full_file_name = file_name + file_extension

            # save picture object
            picture.image.save(
                full_file_name, 
                request.FILES['image'], 
                save = False
            )
            picture.save()
            return render_to_response(
                'example/result.html'
                {'result': "Upload success",},
                context_instance = RequestContext(request))


    return render_to_response(
        'example/picture_upload.html',
        {'form':form},
        context_instance = RequestContext(request))

簡單說明上面的code
如果request不是POST，就只回傳form
如果是POST，則把使用者選擇的圖片上傳到系統裡面
檔名的部分我是用uuid，這樣幾乎可以確保檔案名稱不會重複
file_extension是檔案的格式，例如 jpg 或是 png
最後就印出"Upload success"給使用者


picture_upload.html

<form enctype="multipart/form-data" method="post" action="example/picture_upload">
    {% csrf_token %}   
    <table>
        {{form.as_p}}
    </table>
    <input type="submit" value="Submit" id="Save"/>
</form>

result.html

<p> {{ result }} </p>

上傳檔案大概就是這樣，主要就是設定好
MEDIA_ROOT
upload_to
大概就沒問題了


MEDIA_URL的部分是要讓使用者可以讀取或是顯示出上傳的東西
我是設定成
MEDIA_URL = '/multimedia/'
然後再主要的urls.py加上

urlpatterns += patterns('',
    url(r'^multimedia/(?P.*)$', 'django.views.static.serve',
                 {'document_root': settings.MEDIA_ROOT}),

所以我輸入
http://localhost:8000/multimedia/pic/FileName
就可以顯示出我上傳的圖片了

Django -- create a new app - part3

part 1和2已經記錄了如何開一個新的app和urls.py的設定
這一篇就把剩下的部分講完
這邊主要寫view.py和html的部分

首先先連到apps/polls/

cd //var/www/mutarock/apps/polls
vim views.py

首先先來新增一個index，這個可以印出資料庫最近新增的幾個投票

from django.template import Context, loader
from apps.polls.models import Poll
from django.http import HttpResponse

def index(request):
    latest_poll_list = Poll.objects.all().order_by('-pub_date')[:5]
    t = loader.get_template('polls/index.html')
    c = Context({
        'latest_poll_list': latest_poll_list,
    })
    return HttpResponse(t.render(c))

上面的code會抓出最近的5個投票，並且讀取polls/index.html這個templates
並且把投票資訊傳給他顯示

存檔之後執行熟悉的

python manage.py runserver

開啟瀏覽器 http://127.0.0.1:8000/polls 應該會跑出錯誤訊息

TemplateDoesNotExist at /polls/
polls/index.html

這是因為我們還沒有把templates建立起來，我們前面只是設定

移到前兩層，去建立我們的templates資料夾

cd //var/www/mutarock
mkdir templates
cd templates
mkdir polls

目前這個系統的資料夾應該會像

mutarock/
    manage.py
    mutarock/
    apps/    
        polls/
    templates/
        polls/

移到 templates/polls 資料夾去建立我們的index.html

{% if latest_poll_list %}
{% if latest_poll_list %}
    <ul>
    {% for poll in latest_poll_list %}
        <li><a href="/polls/{{ poll.id }}/">{{ poll.question }}</a></li>
    {% endfor %}
    </ul>
{% else %}
    <p>No polls are available.</p>
{% endif %}

這樣就可以順利顯示我們的polls資訊了
其他的細節我就不細講了，教學都還滿仔細的，我覺得自己講不太清楚，所以detail, vote, result直接看教學比較好
教學三，教學四

Django -- create a new app - part2

part1是一些有關models建立以及如何和系統互動
這邊先來記錄一下如何顯示

首先先修改settings.py中的 TEMPLATE_DIRS

cd //var/www/mutarock/mutarock/
vim settings.py

TEMPLATE_DIRS = (
    # Put strings here, like "/home/html/django_templates" or "C:/www/django/templates".
    # Always use forward slashes, even on Windows.
    # Don't forget to use absolute paths, not relative paths.
    os.path.join(os.path.dirname(__file__), '..', 'templates').replace('\\','/'),
)

這個設定主要是告訴django你的模板放在哪裡，我這邊用的是相對路徑
方便將來移植，如果覺得完全不會動到就用絕對路徑也是可以的啦

回到前一層去新增templates資料夾

cd ..
mkdir templates
cd templates/
mkdir polls

我希望每個apps的模板放的地方不一樣，所以多新增一個子資料夾polls
到目前為止準備工作已經差不多了，接下來還有3個部分

• 設定 urls.py
• 編輯 /apps/polls/views.py
• 編輯顯示用的 html

下面先來處理urls.py
這部分有很多不同的做法，你可以把全部的urls路徑都放到主資料夾下面的urls.py
也可以用導向的方式，在每個apps裡面都有自己的urls.py
教學上面的例子，下面兩個做法等價，挑自己喜歡的風格

例子一:
全都放在 //var/www/mutarock/mutarock/urls.py

from django.conf.urls import patterns, include, url

from django.contrib import admin
admin.autodiscover()

urlpatterns = patterns('',
    url(r'^polls/$', 'polls.views.index'),
    url(r'^polls/(?P\d+)/$', 'polls.views.detail'),
    url(r'^polls/(?P\d+)/results/$', 'polls.views.results'),
    url(r'^polls/(?P\d+)/vote/$', 'polls.views.vote'),
    url(r'^admin/', include(admin.site.urls)),
)

例子二
主資料夾負責導向
//var/www/mutarock/mutarock/urls.py

from django.conf.urls import patterns, include, url

from django.contrib import admin
admin.autodiscover()

urlpatterns = patterns('',
    url(r'^polls/', include('apps.polls.urls')),
    url(r'^admin/', include(admin.site.urls)),
)

apps的資料夾負責細節
//var/www/mutarock/apps/polls/urls.py (預設是沒有這個檔案，要自己新增)

from django.conf.urls import patterns, include, url

urlpatterns = patterns('apps.polls.views',
    url(r'^$', 'index'),
    url(r'^(?P\d+)/$', 'detail'),
    url(r'^(?P\d+)/results/$', 'results'),
    url(r'^(?P\d+)/vote/$', 'vote'),
)

之後再browser上面輸入 http://127.0.0.1/polls 系統就會知道要導向到polls的urls.py

• 後面什麼都不接，會去找polls裡面view.py的index 
• 後面接polls的id，找deatils
• 以此類推

urls.py比較基本的概念就是這些，個人比較偏好第2種做法
主資料夾的urls.py看起來會比較整齊
不然開了幾十個apps不就可能會有幾百行在裡面

Django -- admin page

django的admin page相當的強大
可以顯示出來的東西非常多，不過還有很多細節需要去研究

首先先修改 settings.py
把 django.contrib.admin 的註解拿掉

INSTALLED_APPS = (
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.sites',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    # Uncomment the next line to enable the admin:
    'django.contrib.admin',
    # Uncomment the next line to enable admin documentation:
    # 'django.contrib.admindocs',
    'apps.polls',
)

修改urls.py

from django.conf.urls import patterns, include, url

# Uncomment the next two lines to enable the admin:
from django.contrib import admin
import settings

admin.autodiscover()

urlpatterns = patterns('',
    # Examples:
    # url(r'^$', 'mutarock.views.home', name='home'),
    # url(r'^mutarock/', include('mutarock.foo.urls')),

    # Uncomment the admin/doc line below to enable admin documentation:
    # url(r'^admin/doc/', include('django.contrib.admindocs.urls')),

    # Uncomment the next line to enable the admin:
    url(r'^admin/', include(admin.site.urls)),
)

這邊的urlpattern是利用regular expression去表示
所以在domain後面接 admin 就會去開啟admin page
之後新增不同的app和服務之後就會實際了解如何作用

OK之後可以輸入

python manage.py runsever

打開瀏覽器進入你在domain下面的admin page
例如 http://127.0.0.1/admin
應該會看到














OK之後，下一步是把polls app也加進去admin page
這樣就可以方便管理了
先移到polls的資料夾下面並建立admin.py檔案

cd //var/www/mutarock/apps/polls/
vim admin.py

輸入

from polls.models import Poll
from django.contrib import admin

admin.site.register(Poll)

這樣就可以把這個apps註冊到admin page裡面
至於顯示的部分其實非常多樣化，可以依照apps的欄位顯示，或者顯示一些圖片或是縮圖
可以參考一下教學

Django -- create a new app - part1

為了方便管理全部的apps
所以先在外層的mutarock資料夾開一個apps的app
將來這個project裡面全部的app都放進去這裡

cd //var/www/mutarock
python manage.py startapp apps

以後的app都把它放在這麼資料夾下面
下面用tutorial的範例，簡單的投票系統做例子

cd /apps
python ./manage.py startapp polls

目前整個project的資料夾應該像下面這樣

mutarock/
    manage.py
    mutarock/
    apps/    
        polls/

polls則是長這個樣子

polls/
    __init__.py
    models.py
    tests.py
    views.py

models.py主要是這個app的資料型態，例如這個例子裡面有Poll和Choice
Poll 是只個別的投票
Choice 是各個選項
views.py則是一些動作，例如針對request做運算，或是回傳一些資料資料給使用者

實際開始編輯models.py

from django.db import models

class Poll(models.Model):
    question = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

class Choice(models.Model):
    poll = models.ForeignKey(Poll)
    choice = models.CharField(max_length=200)
    votes = models.IntegerField()

其他細節就不多說了，可以去看教學
只記錄下幾個關鍵
建立完新的app之後要記得去啟動他
到專案的資料夾下面

cd //var/www/mutarock/mutarock
vim settings.py

其中一個欄位是INSTALLED_APPS，在這邊把自己的app加進去

INSTALLED_APPS = (
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.sites',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    # Uncomment the next line to enable the admin:
    # 'django.contrib.admin',
    # Uncomment the next line to enable admin documentation:
    # 'django.contrib.admindocs',
    'apps.polls', #這個範例的app
)

OK之後可以利用強大的managa.py去顯示這個app會建立的哪些table有哪些欄位(based on your model)

python manage.py sql polls

確定應該沒有問題之後就輸入

python manage.py syncdb

系統就會實際把table建好


============================================================
PS 建立完之後可以利用

python manage.py shell

這個語法去實際和系統互動 以下是教學提供的幾個例子，我就貼過來自己看

>>> from polls.models import Poll, Choice   # Import the model classes we just wrote.

# No polls are in the system yet.
>>> Poll.objects.all()
[]

# Create a new Poll.
# Support for time zones is enabled in the default settings file, so
# Django expects a datetime with tzinfo for pub_date. Use timezone.now()
# instead of datetime.datetime.now() and it will do the right thing.
>>> from django.utils import timezone
>>> p = Poll(question="What's new?", pub_date=timezone.now())

# Save the object into the database. You have to call save() explicitly.
>>> p.save()

# Now it has an ID. Note that this might say "1L" instead of "1", depending
# on which database you're using. That's no biggie; it just means your
# database backend prefers to return integers as Python long integer
# objects.
>>> p.id
1

# Access database columns via Python attributes.
>>> p.question
"What's new?"
>>> p.pub_date
datetime.datetime(2012, 2, 26, 13, 0, 0, 775217, tzinfo=<utc>)

# Change values by changing the attributes, then calling save().
>>> p.question = "What's up?"
>>> p.save()

# objects.all() displays all the polls in the database.
>>> Poll.objects.all()
[<Poll: Poll object>]

可以看到最後一個例子回傳的東西相當不人性化
看不出來是什麼鬼
所以可以在原來的models.py裡面加一些東西，讓資料顯示更明顯

class Poll(models.Model):
    # ...
    def __unicode__(self):
        return self.question

class Choice(models.Model):
    # ...
    def __unicode__(self):
        return self.choice

教學上面提到，熟悉python的人一般會使用 __str__ 而不是 __unicode__
這邊會建議使用 __unicode__ 是因為django預設是用unicode

Django -- database

安裝 mysql

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install mysql-server mysql-client python-mysqldb python-django

建立一個django用的database

mysql -u root -p
create database djangodb;
exit;

修改settings.py

cd //var/www/mutarock/mutarock/
vim settings.py

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql', # Add 'postgresql_psycopg2', 'mysql', 'sqlite3' or 'oracle'.
        'NAME': 'djangodb',                      # Or path to database file if using sqlite3.
        'USER': 'USERNAME',                      # Not used with sqlite3.
        'PASSWORD': 'PASSEORD',                  # Not used with sqlite3.
        'HOST': '',                      # Set to empty string for localhost. Not used with sqlite3.
        'PORT': '',                      # Set to empty string for default. Not used with sqlite3.
    }
}

ENGINE: 是database的種類，我是用mysql
NAME: database名稱
USER & PASSWORD: 該資料庫的使用者，如果不是使用root的話要記得放寬權限，不然syncdb的時候會有錯誤訊息

同步資料庫
輸入指令

python manage.py syncdb

就會在所選擇的database裡面新增幾個基本的table
之後開始寫app，也是利用這個指令將app所需要的table建立在database裡面
應該也會要求建立一個登入用的帳號

Django -- install/setup

參考 https://docs.djangoproject.com/en/dev/intro/tutorial01/ ~ /tutorial04/

Install:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install python-setuptools
sudo apt-get install python-pip
sudo pip install django

Create a project:

cd //var/www/
sudo django-admin.py startproject mutarock

資料夾hello長的像這樣~~

mutarock/
    manage.py
    mutarock/
        __init__.py
        settings.py
        urls.py
        wsgi.py

• 各別檔案和資料夾的敘述請見(連結)

確認一下django的server是否正確:

python manage.py runserver

如果沒有問題的話，應該就可以看到
----------------------------------------------------------------
Validating models...
0 errors found.

Django version 1.4, using settings 'mysite.settings'
Development server is running at http://127.0.0.1:8000/
Quit the server with CONTROL-C.
----------------------------------------------------------------
打開瀏覽器
http://127.0.0.1:8000
可以看到預設的頁面

Grid Walk

Challenge Description
There is a monkey which can walk around on a planar grid. The monkey can move one space at a time left, right, up or down. That is, from (x, y) the monkey can go to (x+1, y), (x-1, y), (x, y+1), and (x, y-1). Points where the sum of the digits of the absolute value of the x coordinate plus the sum of the digits of the absolute value of the y coordinate are lesser than or equal to 19 are accessible to the monkey. For example, the point (59, 79) is inaccessible because 5 + 9 + 7 + 9 = 30, which is greater than 19. Another example: the point (-5, -7) is accessible because abs(-5) + abs(-7) = 5 + 7 = 12, which is less than 19. How many points can the monkey access if it starts at (0, 0), including (0, 0) itself?

InputThere is no input for this program.

Output
Print out the how many points can the monkey access. (The number should be printed as an integer whole number eg.
if the answer is 10 (its not !!), print out 10, not 10.0 or 10.00 etc)

exist = []
point = {}

#make sure the sum of digit is less or equal than 19
def belowUpper(x, y):
    if x<0 or y<0:
        return False
    abs_x = str(abs(x))
    abs_y = str(abs(y))
    sum_x = 0
    sum_y = 0
    for c in abs_x:
        sum_x = sum_x + int(c)
    for c in abs_y:
        sum_y = sum_y + int(c)

    if sum_x + sum_y <= 19:
        return True



#check the point is valid or not
def addToList(x, y):
    if belowUpper(x+1, y):
        tmp = str(x+1) + " " + str(y)
        try:
            point[tmp]
        except:
            point[tmp] = 1
            exist.append([x+1, y])
        
        
    if belowUpper(x, y+1):
        tmp = str(x) + " " + str(y+1)
        try:
            point[tmp]
        except:
            point[tmp] = 1
            exist.append([x, y+1])




#remove overlap part when x = 0 or y = 0
def removeOverlap(x, y):
    total = 0
    xx = x
    yy = y
    while True:
        if belowUpper(xx, yy):
           total += 1
           xx += 1
        else:
            break

    return total
    

#main function
exist.append([0,0])

start = 0

while True:
    addToList(exist[start][0],exist[start][1])
    start+=1
    if start >= len(exist):
        break

over = removeOverlap(0, 0)

print (len(exist) - (over)) * 4 + 1

ACM 10062 -- Tell me the frequencies!

#include <iostream>

using namespace std;
void checkunique(string str);
bool first;

int main()
{
    string input;
    first = true;
    //while(cin>>input)
    while(getline(cin, input)){
        if(first == false)
            cout<<endl;
        checkunique(input);
        first = false;
    }
    return 0;
}


void checkunique(string str){
    int char_set[256] = {0};
    for(int i = 0 ; i < str.length() ; i ++){
        int val = str[i];
  char_set[val]++;

    }

    for(int i = 1 ; i <= str.length() ; i ++){
        for(int j = 256 ; j >= 0 ; j--){
            if(char_set[j] == i){
                cout<<j<<" "<<i<<endl;
            }
        }
    }
}