feat(581-shortest-unsorted-continuous-subarray): add py3 solution

0581_shortest-unsorted-continuous-subarray/python3/solution.py

@@ -0,0 +1,39 @@
+class Solution:
+    def findUnsortedSubarray(self, nums: List[int]) -> int:
+        min_unsorted = float("inf")
+        max_unsorted = float("-inf")
+        
+        # Find min and max element in the unsorted portion
+        for i, num in enumerate(nums):
+            if not self.is_sorted(i, nums):
+                min_unsorted = min(min_unsorted, num)
+                max_unsorted = max(max_unsorted, num)
+        
+        if min_unsorted == float("inf"):
+            return 0
+        
+        # Find right places for min and max elements from previous
+        # step in the "sorted" section of the array
+        left = 0
+        while nums[left] <= min_unsorted:
+            left += 1
+            
+        right = len(nums) - 1
+        while nums[right] >= max_unsorted:
+            right -= 1
+        
+        return right - left + 1
+    
+    def is_sorted(self, i: int, nums: List[int]) -> bool:
+        n = len(nums)
+        
+        if n <= 1:
+            return True
+        
+        if i == 0:
+            return nums[i] <= nums[i + 1]
+        
+        if i == n - 1:
+            return nums[i - 1] <= nums[i]
+        
+        return nums[i - 1] <= nums[i] <= nums[i + 1]