【LeetCode】 50. Pow(x, n)（Medium）（JAVA）
Topic Address: https://leetcode.com/problems/powx-n/
Subject description:
Implement pow(x, n), which calculates x raised to the power n (xn).
Example 1:
Input: 2.00000, 10
Output: 1024.00000
Example 2:
Input: 2.10000, 3
Output: 9.26100
Example 3:
Input: 2.00000, -2
Output: 0.25000
Explanation: 2-2 = 1/22 = 1/4 = 0.25
Note:
-100.0 < x < 100.0
n is a 32-bit signed integer, within the range [−2^31, 2^31 − 1]
Subject to the effect
Achieve pow (x, n), i.e., a function of n-th power of x.
Problem-solving approach
Dichotomy, constantly half for multiplication complexity O (logn)
class Solution {
public double myPow(double x, int n) {
if (x == 0) return 0;
if (n == 0) return 1;
if (n == 1) return x;
if (n == -1) return 1 / x;
double half = myPow(x, n / 2);
if (n > 0) {
return n % 2 == 0 ? half * half : half * half * x;
} else {
return n % 2 == 0 ? half * half : half * half / x;
}
}
}
When execution: 1 ms, beat the 97.78% of all users to submit in Java
memory consumption: 37.8 MB, beat the 5.02% of all users to submit in Java
