牛客_雀魂启动！

雀魂启动！
https://www.nowcoder.com/practice/448127caa21e462f9c9755589a8f2416

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;

public class Main {
    private static final int NUM = 13;
    private static final int TOTAL = 14;
    private static final int KIND = 9;

    public static void main(String[] args){
        Scanner in=new Scanner(System.in);

        while(in.hasNext()){
            solution(in);
        }
    }

    /**
     * 模拟法
     * @param in
     */
    private static void solution(Scanner in){
        int[] cards = new int[NUM+1];
        int[] bucket = new int[KIND+1];
        int[] helper = new int[KIND+1];

        for(int i=1; i<=NUM; i++){
            cards[i] = in.nextInt();
            bucket[cards[i]]++;
        }

        List<Integer> result = new ArrayList<>();
        for(int i=1; i<=9; i++){
            if(bucket[i] < 4){
                System.arraycopy(bucket,1, helper,1, KIND);
                // 取当前牌i(第14张牌)
                helper[i]++;
                if(canHu(helper, TOTAL,false)){
                    result.add(i);
                }
            }
        }

        if(result.isEmpty()){
            System.out.println(0);
        }else{
            System.out.println(result.stream().map(Object::toString).collect(Collectors.joining(" ")));
        }
    }

    /**
     * 回溯
     * @param helper
     * @param total
     * @param hasHead
     * @return
     */
    private static boolean canHu(int[] helper, int total, boolean hasHead){
        // 胡牌: 即可以将14张牌匹配得剩下0张
        if(total == 0){
            return true;
        }

        // 先确定雀头
        if(!hasHead){
            for(int i=1; i<=9; i++){
                // 雀头: 大于等于2
                if(helper[i] >= 2){
                    helper[i] -= 2;
                    if(canHu(helper,total-2,true)){
                        return true;
                    }
                    helper[i] += 2;
                }
            }
            return false;
        }else{
            // 有雀头
            for(int i=1; i<=9; i++){
                if(helper[i] > 0){
                    // 匹配刻子
                    if(helper[i] >= 3){
                        helper[i] -= 3;
                        if(canHu(helper,total-3, true)){
                            return true;
                        }
                        helper[i] += 3;
                    }

                    // 匹配顺子
                    if(i+2<=9 && helper[i+1]>0 && helper[i+2]>0){
                        helper[i]--;
                        helper[i+1]--;
                        helper[i+2]--;
                        if(canHu(helper,total-3, true)){
                            return true;
                        }
                        helper[i]++;
                        helper[i+1]++;
                        helper[i+2]++;
                    }
                }
            }
        }
        
        return false;
    }
}