Remove All Adjacent Duplicates In String

Author: anantkaushik

1047-remove-all-adjacent-duplicates-in-string.py

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+"""
+Problem Link: https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/
+
+Given a string S of lowercase letters, a duplicate removal consists of choosing two adjacent 
+and equal letters, and removing them.
+We repeatedly make duplicate removals on S until we no longer can.
+Return the final string after all such duplicate removals have been made. 
+It is guaranteed the answer is unique.
+
+Example 1:
+Input: "abbaca"
+Output: "ca"
+Explanation: 
+For example, in "abbaca" we could remove "bb" since the letters are adjacent and equal, 
+and this is the only possible move.  The result of this move is that the string is "aaca", 
+of which only "aa" is possible, so the final string is "ca".
+ 
+Note:
+1 <= S.length <= 20000
+S consists only of English lowercase letters.
+"""
+class Solution:
+    def removeDuplicates(self, S: str) -> str:
+        stack = []
+        for c in S:
+            if not stack or stack[-1] != c:
+                stack.append(c)
+            else:
+                stack.pop()
+        return "".join(stack)