algorithm-class/大厂刷题班/class29/Problem_0050_PowXN.java

package class29;

public class Problem_0050_PowXN {

	public static int pow(int a, int n) {
		int ans = 1;
		int t = a;
		while (n != 0) {
			if ((n & 1) != 0) {
				ans *= t;
			}
			t *= t;
			n >>= 1;
		}
		return ans;
	}

	// x的n次方，n可能是负数
	public static double myPow(double x, int n) {
		if (n == 0) {
			return 1D;
		}
		int pow = Math.abs(n == Integer.MIN_VALUE ? n + 1 : n);
		double t = x;
		double ans = 1D;
		while (pow != 0) {
			if ((pow & 1) != 0) {
				ans *= t;
			}
			pow >>= 1;
			t = t * t;
		}
		if (n == Integer.MIN_VALUE) {
			ans *= x;
		}
		return n < 0 ? (1D / ans) : ans;
	}

}