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# \[LeetCode] 50. Pow(x, n)

Implement [pow(*x*, *n*)](http://www.cplusplus.com/reference/valarray/pow/), 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]

**Analyse:**

​

**Solution:**

```swift
class Solution { 
    
    func myPow(_ x: Double, _ n: Int) -> Double {
        var base = x;
        var pow = n;
    
        if pow == 0 {
            return 1;
        }
        else if pow < 0 {
            pow = -pow;
            base = 1/base;
        }
    
        if pow % 2 == 0 {
            return myPow(base * base, pow/2);
        }
        else {
            return base * myPow(base * base, pow/2);
        }
    }
}
```