Is Remove All Adjacent Duplicates In String easy or hard?

LeetCode classifies this problem as Easy with an acceptance rate around 70%+. The logic is simple once you recognize the stack pattern. The main challenge for beginners is realizing that removing pairs can trigger new adjacent duplicates.

Remove All Adjacent Duplicates In String Python/Java solution

In Python or Java, iterate through the string and maintain a stack (list or StringBuilder). Compare the current character with the last stored character. If they match, remove the last element; otherwise append the new character. This produces the final string in O(n) time.

How to solve Remove All Adjacent Duplicates In String in O(n)?

Use a stack or simulate one with two pointers. Traverse the string and compare each character with the last inserted character in the result. If they match, remove the previous character; otherwise append the new character. Because each character participates in at most one push and one pop, the algorithm runs in O(n) time.

What is the best approach for Remove All Adjacent Duplicates In String?

The stack-based approach is the most common and intuitive solution. Iterate through the string and push characters onto a stack. If the current character matches the stack's top element, pop it instead of pushing. Each character is processed once, resulting in O(n) time and O(n) space complexity.

Is Remove All Adjacent Duplicates In String asked at Google/Amazon/Meta?

String and stack problems like this frequently appear in interviews at companies such as Amazon, Google, and Meta. Variations include removing k adjacent duplicates or repeatedly collapsing groups of characters. Interviewers use it to test stack reasoning and in-place string manipulation.

What data structure is used in Remove All Adjacent Duplicates In String?

The primary data structure is a stack. It tracks the current valid sequence of characters while scanning the string. Some optimized implementations avoid an explicit stack and instead simulate it using a character array with two pointers.

What is the time complexity of Remove All Adjacent Duplicates In String?

The optimal solutions run in O(n) time, where n is the length of the string. Each character is pushed and popped at most once in the stack approach. The two-pointer method also scans the string once, so the total processing time remains linear.

Description Hints 1 Solution Video 8:10

1047. Remove All Adjacent Duplicates In String

Easy74.2% acceptance15 companies

You are given a string s consisting of lowercase English 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 can be proven that the answer is unique.

Example 1:

Input: s = "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".

Example 2: