二分查找：

二分查找又称折半查找，优点是比较次数少，查找速度快，平均性能好；其缺点是要求待查表为有序表，且插入删除困难。

代码不多也就几行；主要 start = 0； end = nLength -1;while(start <= end);

#include <iostream>using namespace std; /* run this program using the console pauser or add your own getch, system("pause") or input loop */int bianrySearch(int a[], int nLength, int val){	int start = 0;	int end = nLength - 1;	int index = -1;	while(start<=end)	{		index = (start+ end)/2;		if(a[index] == val)		{			return index;		}		else if(a[index] < val)		{			start = index + 1;		}		else		{			end = index -1;		}	}		return -1;}int main(int argc, char** argv) {		int a[] = {0,1,2,3,4,5};	for(int i = 0; i < 6; i++)	{		cout<<a[i]<<"";	}	int k =bianrySearch(a,sizeof(a)/sizeof(int),5);	cout<<"5在的位置为：";	cout<<k<<endl;	return 0;}

C++算法之 二分查找