折半查找

#include "stdafx.h"
#include<iostream>
#include <time.h>
using namespace std;
#pragma warning(disable:4996)
void HalfSearch(int num[], int left, int right, int nData)
{
	int Mid = (right + left) / 2;
	if (left == right){
		return;
	}
	if (num[Mid] == nData){
		printf("%d\n", Mid);
		return;
	}
	if (num[Mid] >= nData){
		HalfSearch(num, left, Mid, nData);
	}
	else{
		HalfSearch(num, Mid, right, nData);
	}
}

int _tmain(int argc, _TCHAR* argv[])
{
	int num[9] = {1, 6, 9 , 12, 18, 20, 40, 55, 61};
	HalfSearch(num, 0, 9, 12);
	return 0;
}

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。因此，折半查找方法适用于不经常变动而查找频繁的有序列表