二分法查找

二分查找

/*折半查找，二分查找*/
//已经排好序的数组中进行查询
#include<stdio.h>
int main(){
	int low, high, mid, userInput;//high low mid 记录的是数组下标
	int flag = 0;//记录能否找到
	int a[10] = {12,14,21,35,48,57,69,78,89,99};//二分查找的前提：已经有序
	low = 0;
	high = 9;
	scanf("%d",&userInput);
	while(low != high){//最小最大的下标不等，continue
		mid = (low + high) / 2;//二分查找，有点递归的意思了？
		if(a[mid] == userInput){
			flag = 1;
			printf("找到了!");
			break;
		}else if(userInput > a[mid]){
			low = mid;//输入的数字大于中间下标对应的值，更新下限low = mid
		}else{
			high = mid;//输入的数字小于中间下标对应的值，更新上限high = mid
		}	
	}
	if(flag == 0){//一定小心，是==，不要搞成赋值了
		printf("Not Found!");
	}	
	return 0;
}