Create check-if-word-is-valid-after-substitutions.py

Author: kamyu104

Python/check-if-word-is-valid-after-substitutions.py

@@ -0,0 +1,20 @@
+# Time:  O(n)
+# Space: O(n)
+
+class Solution(object):
+    def isValid(self, S):
+        """
+        :type S: str
+        :rtype: bool
+        """
+        stack = []
+        for i in S:
+            if i == 'c':
+                if stack[-2:] == ['a', 'b']:
+                    stack.pop()
+                    stack.pop()
+                else:
+                    return False
+            else:
+                stack.append(i)
+        return not stack