最多牌组数

import java.util.*;
import java.util.stream.Collectors;

/**
 * This method finds the maximum number of valid Mahjong groups (either sequences or triplets)
 * that can be formed from the given tiles using Java Streams.
 * 
 * @param tiles an array of integers representing the Mahjong tiles
 * @return the maximum number of valid groups
 */
public class MahjongGroupsStream {
    public static int maxGroups(int[] tiles) {
        // Count the frequency of each tile
        Map<Integer, Long> tileCount = Arrays.stream(tiles)
                                             .boxed()
                                             .collect(Collectors.groupingBy(e -> e, Collectors.counting()));
        List<Integer> sortedTiles = Arrays.stream(tiles)
                                           .boxed()
                                           .sorted()
                                           .collect(Collectors.toList());
        int groups = 0;
        for (int tile : sortedTiles) {
            if (tileCount.get(tile) > 0) {
                // Try to form a triplet (3 of the same)
                if (tileCount.get(tile) >= 3) {
                    tileCount.put(tile, tileCount.get(tile) - 3);
                    groups++;
                } else if (tileCount.get(tile) > 0 && tileCount.getOrDefault(tile + 1, 0L) > 0 && tileCount.getOrDefault(tile + 2, 0L) > 0) {
                    // Try to form a sequence (3 consecutive numbers)
                    tileCount.put(tile, tileCount.get(tile) - 1);
                    tileCount.put(tile + 1, tileCount.get(tile + 1) - 1);
                    tileCount.put(tile + 2, tileCount.get(tile + 2) - 1);
                    groups++;
                }
            }
        }
        return groups;
    }
    public static void main(String[] args) {
        int[] tiles1 = {2, 2, 2, 3, 4};
        int[] tiles2 = {2, 2, 2, 3, 4, 1, 3};
        System.out.println(maxGroups(tiles1)); // Output: 1
        System.out.println(maxGroups(tiles2)); // Output: 2
    }
}