C--二分搜索

//二分搜索
   //时间复杂度小 log2 n
int search(int key, int a[], int len)
{
    int ret = -1;
    int left = 0;
    int right = len-1;
    int mid;
    while(left<right)
    {
        mid = (right + left)/2;
        if(a[mid] == key)
        {
            ret = mid;
            break;
        }else if(a[mid] >key){
            right  = mid-1;
        }else{
            left = mid-1;
        }
    }
    return ret;
}
int main()
{
    int a[] = {1,2,3,4,5};
    int r = search(1, a, sizeof(a)/sizeof(a[0]));
    printf("%d",r);
    return 0;
}