Merge pull request #2609 from Dhyan-P-Shetty/main

Create: 0456-132-pattern.py, Create: 0946-validate-stack-sequences.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

python/0946-validate-stack-sequences.py

@@ -0,0 +1,13 @@
+class Solution(object):
+    def validateStackSequences(self, pushed, popped):
+        i = 0
+        stack = []
+        for n in pushed:
+            stack.append(n)
+            while i < len(popped) and stack and popped[i] == stack[-1]:
+                stack.pop()
+                i += 1
+
+        return not stack
+
+