g2301_2400.s2370_longest_ideal_subsequence.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g2301_2400.s2370_longest_ideal_subsequence;

// #Medium #String #Hash_Table #Dynamic_Programming
// #2022_08_15_Time_28_ms_(85.71%)_Space_48.6_MB_(85.71%)

/**
 * 2370 - Longest Ideal Subsequence\.
 *
 * Medium
 *
 * You are given a string `s` consisting of lowercase letters and an integer `k`. We call a string `t` **ideal** if the following conditions are satisfied:
 *
 * *   `t` is a **subsequence** of the string `s`.
 * *   The absolute difference in the alphabet order of every two **adjacent** letters in `t` is less than or equal to `k`.
 *
 * Return _the length of the **longest** ideal string_.
 *
 * A **subsequence** is a string that can be derived from another string by deleting some or no characters without changing the order of the remaining characters.
 *
 * **Note** that the alphabet order is not cyclic. For example, the absolute difference in the alphabet order of `'a'` and `'z'` is `25`, not `1`.
 *
 * **Example 1:**
 *
 * **Input:** s = "acfgbd", k = 2
 *
 * **Output:** 4
 *
 * **Explanation:** The longest ideal string is "acbd". The length of this string is 4, so 4 is returned. Note that "acfgbd" is not ideal because 'c' and 'f' have a difference of 3 in alphabet order.
 *
 * **Example 2:**
 *
 * **Input:** s = "abcd", k = 3
 *
 * **Output:** 4
 *
 * **Explanation:** The longest ideal string is "abcd". The length of this string is 4, so 4 is returned.
 *
 * **Constraints:**
 *
 * *   1 <= s.length <= 10⁵
 * *   `0 <= k <= 25`
 * *   `s` consists of lowercase English letters.
**/
@SuppressWarnings("java:S135")
public class Solution {
    public int longestIdealString(String s, int k) {
        int ans = 1;
        int[] array = new int[26];
        for (int i = 0; i < s.length(); i++) {
            int curr = s.charAt(i) - 'a';
            int currans = 1;
            int temp = k;
            array[curr] += 1;
            int j = curr - 1;
            while (temp > 0) {
                if (j == -1) {
                    break;
                }
                currans = Math.max(currans, array[j] + 1);
                temp--;
                if (j == 0) {
                    break;
                }
                j--;
            }
            temp = k;
            j = curr + 1;
            while (temp > 0) {
                if (j == 26) {
                    break;
                }
                currans = Math.max(currans, array[j] + 1);
                temp--;
                if (j == 25) {
                    break;
                }
                j++;
            }
            array[curr] = Math.max(currans, array[curr]);
            ans = Math.max(ans, array[curr]);
        }
        return ans;
    }
}