Question

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 [−231, 231 − 1]

Difficulty:Medium

Category:Math, Binary-Search

Analyze

使用分治法,解决求解一半的情况: double half = power(x, n/2);

Solution

class Solution {
 public:
  double myPow(double x, int n) {
    if (n < 0) return 1 / power(x, -n);
    return power(x, n);
  }

  double power(double x, int n) {
    if (n == 0) return 1;
    double half = power(x, n / 2);
    if (n % 2 == 0)
      return half * half;
    else
      return x * half * half;
  }
};
By guozetang            Updated: 2020-09-19 13:02:30

results matching ""

    No results matching ""