Today I have done leetcode's July LeetCoding Challenge with cpp.

July LeetCoding Challenge 24

Description

Pow(x, n)

Implement pow(x, n), which calculates x raised to the power n (i.e., xn).

Example 1:

Input: x = 2.00000, n = 10
Output: 1024.00000

Example 2:

Input: x = 2.10000, n = 3
Output: 9.26100

Example 3:

Input: x = 2.00000, n = -2
Output: 0.25000
Explanation: 2-2 = 1/22 = 1/4 = 0.25

Constraints:

• -100.0 < x < 100.0
• -231 <= n <= 231-1
• n is an integer.
• Either x is not zero or n > 0.
• -104 <= xn <= 104

Solution

template <typename T> int sgn(T val) {
  return (T(0) < val) - (val < T(0));
}
class Solution {
public:
  double myPow(double x, int n) {
    int sign = sgn(n);
    n = abs(n);
    double result = 1;
    double base = x;
    while(n) {
      if(n & 1) result *= base;
      base *= base;
      n /= 2;
    }
    return sign == -1 ? 1 / result : 1 * result;
  }
};

// Accepted
// 306/306 cases passed (4 ms)
// Your runtime beats 40.18 % of cpp submissions
// Your memory usage beats 62.65 % of cpp submissions (5.9 MB)