946. Validate Stack Sequences

Author: Partho Biswas

README.md

@@ -257,6 +257,7 @@ I have solved quite a number of problems from several topics. See the below tabl
 |09| **[173. Binary Search Tree Iterator](https://tinyurl.com/wp2o8h2)** | [Python](https://tinyurl.com/wu6rdaw/173_Binary_Search_Tree_Iterator.py), [Swift](https://tinyurl.com/wuja3c4/173_Binary_Search_Tree_Iterator.swift)| [Vid 1](https://tinyurl.com/vb62v3q), **[Art 1](https://tinyurl.com/smu9ku3)** | Medium | TODO: Check again. Very Important. Learned new things |
 |10| **[284. Peeking Iterator](https://tinyurl.com/wp2o8h2)** | [Python](https://tinyurl.com/wu6rdaw/284_Peeking_Iterator.py), [Swift](https://tinyurl.com/wuja3c4/284_Peeking_Iterator.swift)| **[Art 1](https://tinyurl.com/wv4ufcz)** | Medium | --- |
 |11| **[281. Zigzag Iterator](https://tinyurl.com/rxgn345)** | [Python](https://tinyurl.com/wu6rdaw/281_Zigzag_Iterator.py), [Swift](https://tinyurl.com/wuja3c4/281_Zigzag_Iterator.swift)| **[Art 1](https://tinyurl.com/wv4ufcz)** | Medium | --- |
+|12| **[946. Validate Stack Sequences](https://tinyurl.com/u8wbaqp)** | [Python](https://tinyurl.com/wu6rdaw/946_Validate_Stack_Sequences.py), [Swift](https://tinyurl.com/wuja3c4/946_Validate_Stack_Sequences.swift)| **[Art 1](https://tinyurl.com/um2r3bf)**, **[Art 2](https://tinyurl.com/vc5wmlj)** | Medium | --- |
 
 </p>
 </details>

leetcode.com/python/946_Validate_Stack_Sequences.py

@@ -0,0 +1,29 @@
+# Time and space both O(n)
+class Solution(object):
+    def validateStackSequences(self, pushed, popped):
+        """
+        :type pushed: List[int]
+        :type popped: List[int]
+        :rtype: bool
+        """
+        stack = []
+        for i in range(len(pushed)):
+            stack.append(pushed[i])
+            while stack and popped and popped[0] == stack[-1]:
+                stack.pop()
+                popped.pop(0)
+        return len(stack) == 0
+
+
+
+
+
+# Time : :(n) | Space: O(1)
+class Solution(object):
+    def validateStackSequences(self, pushed, popped):
+        """
+        :type pushed: List[int]
+        :type popped: List[int]
+        :rtype: bool
+        """
+