不保证ac
题目：
https://www.nowcoder.com/discuss/475166

第一题

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String line = in.nextLine();
        in.close();
        String[] strings = line.split(",");
        int tmp;
        int m5 =0;
        int m10=0;
        for (int i = 0; i < strings.length; i++) {
            tmp = Integer.parseInt(strings[i]);
            if(tmp==5) {
                m5++;
                continue;
            }
            if(tmp==10) {
                m10++;
                m5--;
                if(m5<0){
                    System.out.println("false,"+(i+1));
                    return;
                }else {
                    continue;
                }
            }
            if(tmp==20){
                if(m10>0){
                    m10--;
                    m5--;
                }else{
                    m5=m5-3;
                }
                if(m5<0){
                    System.out.println("false,"+(i+1));
                    return;
                }else {
                    continue;
                }
            }
            System.out.println("false,"+(i+1));
            return;
        }
        System.out.println("true,"+strings.length);
    }
}

第二题

import java.util.Scanner;

public class Main5 {
    static int S,M,N;
    static int[][] direction = {{0,1},{0,-1},{1,0},{-1,0}};

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        S = in.nextInt();
        M = in.nextInt();
        N = in.nextInt();
        int[][] graph = new int[M][N];

        for (int i = 0; i < M; i++) {
            for (int j = 0; j < N; j++) {
                graph[i][j] = in.nextInt();
            }
        }
        in.close();

        if(graph[M-1][N-1]==0){
            System.out.println(0);
            return;
        }
        dfs(graph,0,0);

        if(graph[M-1][N-1]==0){
            System.out.println(1);
        }
    }

    static void dfs(int[][] graph, int i,int j){
        if(i<0||i>=M||j<0||j>=N) {
            return;
        }
        if(graph[i][j] == 0){
            return;
        }
        graph[i][j] = 0;
        for (int k=0;k<4;k++){
            i += direction[k][0]*S;
            j += direction[k][1]*S;
            dfs(graph,i,j);
        }
    }
}

第三题

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String line = in.nextLine();
        in.close();

        String[] strings=line.split(",");
        String str=strings[0];
        int odd=Integer.valueOf(strings[1]);

        StringBuilder[] builders = new StringBuilder[odd];
        for (int j = 0; j < odd; j++) {
            builders[j] = new StringBuilder();
        }

        int rowNumber = 0;
        int index = 0;
        int length = str.length();

        while(index<length){
            for (int i = 0; i < odd; i++) {
                if(rowNumber==i||(rowNumber+i+1)==odd) {
                    builders[i].append(str.charAt(index++));
                    if(index==length) break;
                }
            }
            rowNumber=(rowNumber+1)%(odd-1);
        }

        for (int i = 0; i < odd ; i++) {
            System.out.print(builders[i]);
        }

    }
}