LeetCode 3503: Longest Palindrome After Substring Concatenation I Solution

Master LeetCode problem 3503 (Longest Palindrome After Substring Concatenation I), 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.

3503. Longest Palindrome After Substring Concatenation I

Medium

Two Pointers String Dynamic Programming Enumeration

Problem Explanation

Explanation

To find the longest palindrome that can be formed by concatenating substrings from strings s and t, we can iterate through all possible substrings of s and t, concatenate them, and check if the resulting string is a palindrome. If it is a palindrome, we update the maximum length found so far. We need to check all possible substrings because a palindrome can be formed by selecting different parts from s and t.

Algorithm:

Iterate through all possible substrings of s and t.
For each pair of substrings, concatenate them and check if the resulting string is a palindrome.
If it is a palindrome and longer than the current maximum length, update the maximum length.
Return the maximum length found.

Time Complexity:

The time complexity of this approach is O(n^4), where n is the maximum length of s and t. This is because we are iterating through all possible substrings of s and t and for each pair, checking if the concatenated string is a palindrome.

Space Complexity:

The space complexity is O(1) as we are not using any extra space proportional to the input size.

Solution Code

class Solution {
    public int longestPalindrome(String s, String t) {
        int maxLen = 0;
        for (int i = 0; i <= s.length(); i++) {
            for (int j = 0; j <= t.length(); j++) {
                String concat = s.substring(0, i) + t.substring(0, j);
                if (isPalindrome(concat)) {
                    maxLen = Math.max(maxLen, concat.length());
                }
            }
        }
        return maxLen;
    }

    private boolean isPalindrome(String str) {
        int left = 0, right = str.length() - 1;
        while (left < right) {
            if (str.charAt(left) != str.charAt(right)) {
                return false;
            }
            left++;
            right--;
        }
        return true;
    }
}

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