题解 | #走方格的方案数#

方法一 DFS深度优先

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static int result = 0;
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int a = in.nextInt();
            int b = in.nextInt();
            find(a, b, 0, 0);
            System.out.println(find2(a, b));
        }
    }
  /**
  DFS 深度优先
  */
    public static void find(int a, int b, int cow, int row) {
        if (cow == a && row == b) {
            result = result + 1;
            return;
        }
        if (cow + 1 <= a) {
            find(a, b, cow + 1, row);
        }
        if (row + 1 <= b) {
            find(a, b, cow, row + 1);
        }
    }
  
  /**
  动态，规划
  */
    public static int find2(int a, int b) {
        int[][] dp = new int[a + 1][b + 1];
        dp[0][0] = 0;
        for (int i = 0; i <= a; i++) {
            for (int j = 0; j <= b; j++) {
                if (i == 0 || j == 0) {
                    dp[i][j] = 1;
                } else {
                    dp[i][j] = dp[i][j - 1] + dp[i - 1][j];
                }
            }
        }
        return dp[a][b];
    }
}