feat(189-rotate-array): add py3 solution

0189_rotate-array/README.md

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+Given an array, rotate the array to the right by `k` steps, where `k` is non-negative.
+
+**Example 1:**
+
+    Input: nums = [1,2,3,4,5,6,7], k = 3
+    Output: [5,6,7,1,2,3,4]
+    Explanation:
+    rotate 1 steps to the right: [7,1,2,3,4,5,6]
+    rotate 2 steps to the right: [6,7,1,2,3,4,5]
+    rotate 3 steps to the right: [5,6,7,1,2,3,4]
+    
+
+**Example 2:**
+
+    Input: nums = [-1,-100,3,99], k = 2
+    Output: [3,99,-1,-100]
+    Explanation: 
+    rotate 1 steps to the right: [99,-1,-100,3]
+    rotate 2 steps to the right: [3,99,-1,-100]
+    
+
+**Constraints:**
+
+*   `1 <= nums.length <= 105`
+*   `-231 <= nums[i] <= 231 - 1`
+*   `0 <= k <= 105`
+
+**Follow up:**
+
+*   Try to come up with as many solutions as you can. There are at least **three** different ways to solve this problem.
+*   Could you do it in-place with `O(1)` extra space?

0189_rotate-array/python3/extra_space.py

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+# Time: O(N)
+# Space: O(N)
+class Solution:
+    def rotate(self, nums: List[int], k: int) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        n = len(nums)
+        result = [None] * n
+        
+        for i, num in enumerate(nums):
+            new_i = (i + k) % n
+            result[new_i] = num
+            
+        for i, num in enumerate(nums):
+            nums[i] = result[i]