二分查找and快速排序

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二分查找：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
//法一，非递归实现
int second_find(int *L,int key,int low,int sizearray)
{
    int mid = 0;
    int high = sizearray - 1;
    while(low <= high)
    {
        mid = (low + high)/2
        if (key < L[mid])
        {
            high = mid - 1;
        }
        else if (key > L[mid])
        {
            low = mid + 1;
        }
        else
        {
            return mid;
        }
    }
}
//法二,递归实现
int send_find2(int *L,int key,int low,int high)
{
    if (low <= high)
    {
        int mid = (low+high)/2;
        if (key < L[mid])
        {
            send_find2(L,key,low,mid -1);
        }
        else if(key > L[mid])
        {
            send_find2(L,key,mid + 1,high);
        }
        else
        {
            return mid;
        }
    }
    else 
    {
        return -1;
    }
}

int main(int argc,char *argv)
{
    int a[5] = {1,2,3,4,5};
    int num = second_find(a,2,0,sizeof(a)/sizeof(a[0]));
}

快速排序：

int paintion(int *L,int low,int high)
{
    int poit = L[low];
    while(low < high)
    {
        while(low < high && L[low] <= poit)
            low++;
        swap(L,low,high);
        while(low < high && L[high] >= poit)
            high--;
        swap(L,low,high);
    }
    return low;
}
void Qsort(int *L,int low,int high)
{
    int poit = 0;
    if (low < high)
    {
        poit = paintion(L,low,high);
        Qsort(L,poit+1,high);
        Qsort(L,low,poit - 1);
    }
}
int main(int argc,char *argv[])
{

    return 0;
}

快速排序优化

#include <stdio.h>

int paintion(int *L,int low,int high)
{
    int poit = L[low];
    while(low < high)
    {    
         while(low < high && L[high] >= poit)
            high--;
         L[low] = L[high];
         while(low < high && L[low] <= poit)
            low++; 
         L[high] = L[low];
    }
    L[low] = poit;
    return low;
}

void  Qsort(int *L,int low,int high)
{
    if (low < high)
    {
        int poit = paintion(L,low,high);
        Qsort(L,low,poit - 1);
        Qsort(L,poit + 1,high);
    }
}

int main(int argc,char *argv[])
{
    int a[20] = {10,9,16,3,17,7,19,20,11,1,15,12,4,5,14,2,6,18,8,13};
    Qsort(a,0,19);
    int i = 0;
    for (;i<20;i++)
    {
        printf("a:%d\n",a[i]);
    }
    return 0;
}