单字符重复子串的最大长度

/*
 * Problem Statement: Given a string text, you can swap two characters once or do nothing to form substrings of repeated characters. Return the length of the longest such substring.
 * 
 * Approach using Java Stream:
 * 1. Use a stream to create groups of consecutive identical characters.
 * 2. Calculate maximum possible lengths similar to the standard approach.
 * 3. Return the maximum length found.
 */
import java.util.*;
import java.util.stream.Collectors;

public class Solution {
    public int maxRepOpt1(String text) {
        int n = text.length();
        if (n <= 1) return n;
        Map<Character, Long> countMap = text.chars().mapToObj(c -> (char)c)
            .collect(Collectors.groupingBy(c -> c, Collectors.counting()));
        List<int[]> groups = new ArrayList<>();
        int i = 0;
        while (i < n) {
            int j = i;
            while (j < n && text.charAt(j) == text.charAt(i)) j++;
            groups.add(new int[]{text.charAt(i) - 'a', j - i});
            i = j;
        }

        return groups.stream().mapToInt(group -> {
            int currentChar = group[0];
            int groupLen = group[1];
            int maxLen = groupLen;
            if (countMap.get((char)(currentChar + 'a')) > groupLen) {
                maxLen = Math.max(maxLen, groupLen + 1);
            }
            for (int k = 0; k < groups.size() - 2; k++) {
                if (groups.get(k + 1)[1] == 1 && groups.get(k + 2)[0] == currentChar) {
                    maxLen = Math.max(maxLen, groupLen + groups.get(k + 2)[1]);
                    if (countMap.get((char)(currentChar + 'a')) > groupLen + groups.get(k + 2)[1]) {
                        maxLen = Math.max(maxLen, groupLen + groups.get(k + 2)[1] + 1);
                    }
                }
            }
            return maxLen;
        }).max().orElse(0);
    }
}