代码

int binary_search(const unsigned *a, int n, unsigned x)
{
unsigned l=0,r=n-1;
unsigned ret=0,mid;
while(l<=r) {
mid=(l+r)>>1;
if(a[mid]==x) return mid;
if(a[mid]<x) l=mid+1; else r=mid-1;
}
}

评测结果