50. Pow(x, n)

Medium (LinkedIn, Google, Bloomberg, Facebook)

Implement pow(x, n).

public class Solution {

// test case:
// x == 1 or n == 0
// x == -1
// x == 0 or n >= Integer.MAX_VALUE or n <= Integer.MIN_VALUE
// x < 0 or n < 0

public double myPow(double x, int n) {
    if(x == 1 || n == 0) {
        return 1;
    } else if(x == -1) {
        return n % 2 == 0 ? 1 : -1;
    } else if(x == 0 || n >= Integer.MAX_VALUE || n <= Integer.MIN_VALUE) {
        return 0;
    }

    int x_flag = 1;
    int n_flag = n > 0 ? 1 : -1;
    n = Math.abs(n);

    if(x < 0 && n % 2 == 1) {
        x_flag = -1;
    } 

    x = Math.abs(x);
    double sum = 1;

    while(n > 1) {
        if(n % 2 == 1) {
            sum *= x;
        }

        x = x * x;
        n /= 2;
    }

    sum = sum * x * x_flag;

    if(n_flag > 0) {
        return sum;
    } else {
        return 1 / sum;
    }

}