50. Pow(x, n)

1. Description

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

2. Example

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: $2^{-2}$ = $\frac{1}{2^2}$ = $\frac{1}{4}$ = 0.25

3. Constraints

• -100.0 < x < 100.0
• $-2^{31}$ <= n <= $2^{31}-1$
• $-10^4$ <= xn <= $10^4$

4. Solutions

My Accepted Solution

n = exp
Time complexity : O($log_2n$)
Space complexity : O(1)

class Solution {
public:
    double myPow(double x, int n) {
        double base = n > 0 ? x : 1 / x;
        int exp = abs(n);

        double result = 1;
        while (exp > 0) {
            if ((exp & 1) == 1) {
                result *= base;
            }

            base *= base;
            exp >>= 1;
        }

        return result;
    }
};