URAL 1044 Lucky Tickets. Easy!

算是个动态规划，统计和

sum[位数][差值]

构建个虚拟数组写起来就顺多了

 1 import java.util.Scanner;
 2
 3 public class P1044
 4 {
 5     private static int save[][] = new int[10][100];
 6
 7     private static int getSum(int n, int deta)
 8     {
 9         return save[n][deta + 50];
10     }
11
12     private static void addSum(int n, int deta, int sum)
13     {
14         save[n][deta + 50] += sum;
15     }
16
17     public static void main(String args[])
18     {
19         addSum(0, 0, 1);
20         for (int i = 0; i <= 6; i++)
21             for (int deta = -36; deta <= 36; deta++)
22                 if (getSum(i, deta) != 0)
23                     for (int x = 0; x <= 9; x++)
24                         for (int y = 0; y <= 9; y++)
25                             addSum(i + 2, deta + x - y, getSum(i, deta));
26         try (Scanner cin = new Scanner(System.in))
27         {
28             while (cin.hasNext())
29             {
30                 int n = cin.nextInt();
31                 System.out.println(getSum(n, 0));
32             }
33         }
34     }
35 }