add 0456-132-pattern.py

Author: Dhyan-P-Shetty

python/0456-132-pattern.py

@@ -0,0 +1,15 @@
+class Solution:
+    def find132pattern(self, nums: List[int]) -> bool:
+        stack = [] # pair [num, curLeftMin], mono-decreasing stack
+        curMin = nums[0]
+
+        for n in nums:
+            while stack and n >= stack[-1][0]:
+                stack.pop()
+            if stack and n < stack[-1][0] and n > stack[-1][1]:
+                return True
+
+            stack.append([n, curMin]) 
+            curMin = min(n, curMin)
+
+        return False