C++ 判断一个数是不是完全平方数

bool isPerfectSquare(int num) 
{
    int num1 = 1;
    while(num > 0) 
    {
        num -= num1;
        num1 += 2;
    }
    return num == 0;
}

bool isPerfectSquare(int num)
{
    if(num == 1)
        return true;
 
    int start = 2;
    int end = num;
    int mid;
    while(start <= end)
    {
        mid = start + (end - start)/2;
        if(mid == num / mid && num % mid == 0)
            return true;
 
        if(mid > num / mid)
            end = mid - 1;
        else
            start = mid + 1;
    }
        
    return false;
}