50. Pow(x, n)

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50. Pow(x, n)

Description

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

Example 1:

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Input: x = 2.00000, n = 10
Output: 1024.00000

Example 2:

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Input: x = 2.10000, n = 3
Output: 9.26100

Example 3:

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Input: x = 2.00000, n = -2
Output: 0.25000
Explanation: 2^-2 = 1/2^2 = 1/4 = 0.25

Constraints:

  • -100.0 < x < 100.0
  • -2^31 <= n <= 2^31-1
  • n is an integer.
  • Either x is not zero or n > 0.
  • -10^4 <= x^n <= 10^4

Hints/Notes

Solution

Language: C++

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class Solution {
public:
    double myPow(double x, int n) {
        double f = x, res = 1;
        long abs_n = abs((long)n);
        while(abs_n > 0) {
            if (abs_n % 2) {
                res = res * f;
            }
            f = f * f;
            abs_n /= 2;
        }
        return n > 0 ? res : 1 / res;
    }
};