最长理想子序列

// Problem description:
// Given a string s and an integer k, find the length of the longest ideal subsequence in s.
// A subsequence is ideal if the absolute difference between the positions of every two adjacent characters in the subsequence is less than or equal to k.

import java.util.stream.IntStream;

public class LongestIdealSubsequenceStream {
    public int longestIdealString(String s, int k) {
        int[] dp = new int[26];

        s.chars().forEach(c -> {
            int pos = c - 'a';
            int maxLength = IntStream.rangeClosed(Math.max(0, pos - k), Math.min(25, pos + k))
                                   .map(i -> dp[i])
                                   .max()
                                   .orElse(0);
            dp[pos] = maxLength + 1;
        });

        return IntStream.of(dp).max().orElse(0);
    }
}