1047. Remove All Adjacent Duplicates In Stack (Python)

Related Topic

Stack.

Description

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.

Sample I/O

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. 1 <= S.length <= 20000
2. S consists only of English lowercase letters.

Methodology

Iterate the string and append each character to stack, if top of stack is same as current then pop the top out of stack and continue to next iteration. After done iteration, we join all element in stack to 1 string which is the result

    def removeDuplicates(self, S: str) -> str:
        stack = []
        for c in S:
            if stack and stack[-1]==c:
                stack.pop()
                continue
            stack.append(c)
        return ''.join(stack)

BigO

We iterate the string once the time complexity is O(N).