完美的方形和完美的立方体

Question

在c ++中是否有任何预定义的函数来检查数字是否为任何数字的平方并且对于多维数据集是否相同.

Answer 1

不,但写一个很容易:

bool is_perfect_square(int n) {
    if (n < 0)
        return false;
    int root(round(sqrt(n)));
    return n == root * root;
}

bool is_perfect_cube(int n) {
    int root(round(cbrt(n)));
    return n == root * root * root;
}

Answer 2

sqrt(x),或一般来说,pow(x, 1./2)或pow(x, 1./3)

例如:

int n = 9;
int a = (int) sqrt((double) n);
if(a * a == n || (a+1) * (a+1) == n)  // in case of an off-by-one float error
    cout << "It's a square!\n";

编辑:或一般情况下:

bool is_nth_power(int a, int n) {
  if(n <= 0)
    return false;
  if(a < 0 && n % 2 == 0)
    return false;
  a = abs(a);

  int b = pow(a, 1. / n);
  return pow((double) b, n) == a || pow((double) (b+1), n) == a;
}