二分查找

二分查找也叫折半查找。

#include<stdio.h>int search(int arr[],int key,int left,int right){while(left<=right){while(left<=right){int mid=(right+left)/2;if(arr[mid]<key){left=mid+1;}else if(arr[mid]>key){right=mid-1;}else{return mid;}}return -1;}}int main(){int arr[]={0,1,2,3,4,5,6,7,8,9};int key;int left=0;int ret=0;int right=sizeof(arr)/sizeof(arr[0])-1;scanf("%d",&key);        ret=search(arr,key,left,right);if(ret==-1){printf("找不着\n");}else{printf("%d\n",ret);}system("pause");return 0;}