二分查找

#include <iostream>
using namespace std;

int binarySearch(int a[],int n,int key)
{
	int low,high,mid;
	low = 0;
	high = n-1;
	while(low <= high)  //记得这个等号...
	{
		mid = (low + high)/2;
		if (key < a[mid])
			high = mid - 1;
		else if (key > a[mid])
			low = mid + 1;
		else
			return mid;
	}
}

int main(int argc, char const *argv[])
{
	int a[] = {1,1,2,3,5,7,9};
	int pos = binarySearch(a,sizeof(a)/sizeof(int),5);
	cout << pos;
	return 0;
}

来源：oschina

链接：https://my.oschina.net/u/857259/blog/86160