1. 数字三角形

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int[][] dp = new int[n + 1][n + 1];
        int max = 0;
        for (int i = 1; i < dp.length; i++) {
            for (int j = 1; j <= i; j++) {
                dp[i][j] = scan.nextInt();
                dp[i][j] = Math.max(dp[i][j] + dp[i - 1][j], dp[i][j] + dp[i - 1][j - 1]);
                max = Math.max(max, dp[i][j]);
            }
        }  
        System.out.println(max);
    }

}

注意：

1. 定义一个 int[][] dp = new int[n + 1][n + 1];
   大小为n+1,n+1的二维数组
2. for (int i = 1; i < dp.length; i++) {

for (int j = 1; j <= i; j++) {