g1501_1600.s1542_find_longest_awesome_substring.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g1501_1600.s1542_find_longest_awesome_substring;

// #Hard #String #Hash_Table #Bit_Manipulation
// #2022_04_11_Time_12_ms_(84.16%)_Space_47.2_MB_(57.43%)

import java.util.Arrays;

/**
 * 1542 - Find Longest Awesome Substring\.
 *
 * Hard
 *
 * You are given a string `s`. An **awesome** substring is a non-empty substring of `s` such that we can make any number of swaps in order to make it a palindrome.
 *
 * Return _the length of the maximum length **awesome substring** of_ `s`.
 *
 * **Example 1:**
 *
 * **Input:** s = "3242415"
 *
 * **Output:** 5
 *
 * **Explanation:** "24241" is the longest awesome substring, we can form the palindrome "24142" with some swaps.
 *
 * **Example 2:**
 *
 * **Input:** s = "12345678"
 *
 * **Output:** 1
 *
 * **Example 3:**
 *
 * **Input:** s = "213123"
 *
 * **Output:** 6
 *
 * **Explanation:** "213123" is the longest awesome substring, we can form the palindrome "231132" with some swaps.
 *
 * **Constraints:**
 *
 * *   1 <= s.length <= 10⁵
 * *   `s` consists only of digits.
**/
public class Solution {
    public int longestAwesome(String s) {
        int n = s.length();
        int[] idx = new int[(int) Math.pow(2, 10)];
        Arrays.fill(idx, Integer.MAX_VALUE);
        idx[0] = -1;
        int mask = 0;
        int ans = 0;
        for (int i = 0; i < n; i++) {
            mask ^= 1 << (s.charAt(i) - '0');
            ans = Math.max(ans, i - idx[mask]);
            for (int j = 0; j < 10; j++) {
                ans = Math.max(ans, i - idx[mask ^ (1 << j)]);
            }
            idx[mask] = Math.min(idx[mask], i);
        }
        return ans;
    }
}