对有序的数组使用二分查找，可提高效率

二分查找，下标由0开始，递归结束条件，data[p] == key || start >= end

int BinaryS(int *data,int start,int end,int key)
{
    
    int result;
    int p = (start + end) / 2;
    if (data[p] == key || start >= end) {
        if (data[p] == key) {
            result = p;
            printf("\nyes! index is %d\n",p);
            return result;
        }
        else
        {
            result = -1;
            printf("\nno! %d\n",-1);
            return result;
        }
        
        
        //return result;
    }
    
    else
    {
        if (data[p] > key) {
            result =  BinaryS(data, start, p, key);
        }
        else
        {
            result =  BinaryS(data, p + 1, end, key);
        }
        
        return result;
    }
   
}