49. Pow(x, n)

Implement pow(x, n).

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Recursive

divide-and-conquer approach

O(lgn)

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public class Solution {
    
    double pow(double x, int n) {
        if (n == 0) return 1.0;
        // Compute x^{n/2} and store the result into a temporary
        // variable to avoid unnecessary computing
        double half = pow(x, n / 2);
        if (n % 2 == 0)
            return half * half;
        else if (n > 0)
            return half * half * x;
        else
            return half * half / x;
    }
    
}