折半查找法

#include <stdio.h>int halfsearch(int a[],int n,int x);int main(){ int a[10]={4,5,7,8,10,12,16,18,20,30},n,x; scanf("%d",&x); if(n=halfsearch(a,10,x)!=-1)  printf("%d %d",x,n); else  ; return 0;  }int halfsearch(int a[],int n,int x){ int s=0,e=n-1,m; while(s<=e) {  m=(s+e)/2;  if(a[m]==x)   return m;  else if(x>a[m])   s=m+1;  else   e=e-1; } return -1;}