折半查找

<pre name="code" class="cpp">#include<stdio.h>int binsearch(int x,int v[],int n){int left=0;int right=n-1;int mid=0;while(left<=right){mid=(right+left)/2;if(v[mid]==x)return mid;if(v[mid]<x){left=mid+1;}if(v[mid]>x){right=mid-1;}}return -1;}int main(){int a[]={1,2,3,4,5,6,7};int ret=binsearch(3,a,sizeof(a)/sizeof(a[0]));printf("%d\n",ret);return 0;}