求指导下这段二分搜索的代码哪里有问题？

Question

#include<stdio.h>

int search(int key,int a[],int len)
{
int left=0;
int right=len-1;
int ret=-1;
while(left<right){
int mid=(left+right)/2;
if(a[mid]==key){
ret=mid;
break;
}else if(a[mid]<key){
left=mid+1;
}else{
right=mid-1;
}
}
return ret;
}
int main(){
int k=14;
int a[]={1,2,4,9,11,14,17,20,23,25,28,30,34,36,38,39,41,42,46,47,52,54};
int r=search(k,a,sizeof(a)/sizeof(a[0]));
printf("%d",r);
return 0;
}

Answer 1

你这种写法是基于数组有序的前提