5、折半查找（二分查找）

前提条件：数组排序

#include<iostream>

using namespace std;

int BinarySearch(int *a,const int x,const int n);

int main()
{
	int x[]={1,2,3,4,5,6,7,8,9,10};
	int result;
	int num=7;//要找的数

 12 	result=BinarySearch(x,num,10);

	if(result<0)
		cout<<”没找到！”<<endl;
	else
		cout<<"在m["<<result<<"]处找到"<<x[result]<<endl;
	system("pause");
	return 0;
}

int BinarySearch(int *a,const int x,const int n)
{
	int left,right,mid;
	left=0;right=n-1;

	while(left<=right)
	{
		mid=(left+right)/2;
		if(a[mid] == x)
			return mid;
		else if(a[mid] < x)
			left=mid+1;
		else if(a[mid] > x)
			right=mid-1;
	}
	return -1;
}

VS2010中运行结果：