4ac

题目没记

第一题

package xunfei;

import java.util.Scanner;

public class Main1 {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String[] line1 = scanner.nextLine().split(",");
        int M = Integer.parseInt(line1[0]);
        int N = Integer.parseInt(line1[1]);
        int[][] mat = new int[M][N];
        for (int i = 0; i < M; i++) {
            String[] line = scanner.nextLine().split(" ");
            for (int j = 0; j < N; j++) {
                mat[i][j] = Integer.parseInt(line[j]);
            }
        }


        for (int i = M-1; i >=0 ; i--) {
            for (int j = N-1; j >=0 ; j--) {
                if(i==M-1&&j==N-1){
                    continue;
                }
                if(i==M-1){
                    mat[i][j] += mat[i][j+1];
                    continue;
                }
                if(j==N-1){
                    mat[i][j] += mat[i+1][j];
                    continue;
                }

                mat[i][j]+=Math.max(mat[i][j+1],mat[i+1][j]);
            }
        }
        System.out.println(mat[0][0]);

    }

}

第二题

package xunfei;

import java.util.Scanner;

public class Main2 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int M = scanner.nextInt();
        scanner.nextLine();
        String[] str = scanner.nextLine().split(",");
        int[] num = new int[M];
        for (int i = 0; i < M; i++) {
            num[i] = Integer.parseInt(str[i]);
        }



        for (int i = 0; i < M; i++) {
            int max = Integer.MAX_VALUE;
            int index = 0;
            for (int j = i; j < M; j++) {
                if(num[j]<max){
                    max = num[j];
                    index = j;
                }
            }
            swap(num,i,index);
            if(i==M-1){
                System.out.print(num[i]);
            }else{
                System.out.print(num[i]+",");
            }
        }

    }
    static void swap(int[] num, int i, int index){
        if(i==index) return;
        int temp = num[i];
        num[i] = num[index];
        num[index] = temp;
    }
}

第三题

package xunfei;

import java.util.Scanner;

public class Main3 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String line = scanner.nextLine();
        int len = line.length();

        int count = 0;
        for (int i = len-1; i >= 0; i--) {
            if(String.valueOf(line.charAt(i)).equals("_")){
                count++;
            }else{
                break;
            }
        }


        int flag = 0;
        int flagg = 0;
        for (int i = 0; i < len-count; i++) {
            if(String.valueOf(line.charAt(i)).equals("_")){
                if(flag==0){
                    continue;
                }
                if(flagg==0){
                    System.out.print(line.charAt(i));
                    flagg = 1;
                }


            }else {
                flag = 1;
                System.out.print(line.charAt(i));
                flagg = 0;
            }

        }

    }
}

第四题

package xunfei;

import java.util.Scanner;

public class Main4 {
    static int flag = 0;
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int x = scanner.nextInt();

        fun(x);

    }

    private static void fun(int x) {
        if(x==1) return;
        int temp = 1;
        for (int i = 2; i < x+1; i++) {
            if(x%i==0){
                if (flag==0){
                    System.out.print(i);
                    flag = 1;
                }else{
                    System.out.print("*"+i);
                }

                temp = i;
                break;
            }
        }
        fun(x/temp);
    }
}