Added Python solution for "Set Mismatch"

Author: Kyrylo-Ktl

Python/Set Mismatch.py

@@ -0,0 +1,24 @@
+from typing import List
+
+
+class Solution:
+    """
+    Time:   O(n)
+    Memory: O(1)
+    """
+
+    def findErrorNums(self, nums: List[int]) -> List[int]:
+        duplicate = -1
+        missing = 1
+
+        for n in nums:
+            if nums[abs(n) - 1] < 0:
+                duplicate = abs(n)
+            else:
+                nums[abs(n) - 1] *= -1
+
+        for i in range(1, len(nums)):
+            if nums[i] > 0:
+                missing = i + 1
+
+        return [duplicate, missing]