LeetCode 844: Backspace String Compare Solution

Master LeetCode problem 844 (Backspace String Compare), a easy 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.

844. Backspace String Compare

Easy

Two Pointers String Stack Simulation

Problem Explanation

Explanation

To solve this problem, we can use a stack to simulate the typing process for both strings. We iterate over each character in the input strings, and if we encounter a character that is not a backspace ('#'), we push it onto the stack. If we encounter a backspace character, we pop the top character from the stack.

After iterating through both strings, we compare the characters left in the stacks for s and t. If the characters in the stacks are equal, then the strings are equal after applying backspaces.

Time Complexity: O(n) where n is the length of the longer string among s and t. Space Complexity: O(n)

Solution Code

class Solution {
    public boolean backspaceCompare(String s, String t) {
        return buildString(s).equals(buildString(t));
    }
    
    private String buildString(String str) {
        StringBuilder sb = new StringBuilder();
        for (char c : str.toCharArray()) {
            if (c != '#') {
                sb.append(c);
            } else if (sb.length() > 0) {
                sb.deleteCharAt(sb.length() - 1);
            }
        }
        return sb.toString();
    }
}

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