LeetCode 3039: Apply Operations to Make String Empty Solution

Master LeetCode problem 3039 (Apply Operations to Make String Empty), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

3039. Apply Operations to Make String Empty

Medium

Array Hash Table Sorting Counting

Problem Explanation

Explanation

To solve this problem, we can use a stack to keep track of the characters in the string s. We iterate through each character in s and check if it is already in the stack. If it is, we pop all characters in the stack that are equal to the current character. If it is not in the stack, we push it onto the stack. Finally, we construct the result string by popping characters from the stack.

Algorithm:

Initialize an empty stack.
Iterate through each character in the string s.
If the character is already in the stack, pop all characters equal to the current character from the stack.
If the character is not in the stack, push it onto the stack.
Construct the result string by popping characters from the stack.

Time Complexity:

The time complexity of this algorithm is O(n) where n is the length of the input string s.

Space Complexity:

The space complexity is also O(n) where n is the length of the input string s.

Solution Code

class Solution {
    public String makeEmpty(String s) {
        Stack<Character> stack = new Stack<>();
        
        for (char c : s.toCharArray()) {
            if (!stack.isEmpty() && stack.peek() == c) {
                while (!stack.isEmpty() && stack.peek() == c) {
                    stack.pop();
                }
            } else {
                stack.push(c);
            }
        }
        
        StringBuilder result = new StringBuilder();
        while (!stack.isEmpty()) {
            result.insert(0, stack.pop());
        }
        
        return result.toString();
    }
}

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