HDU 2510 - 符号三角形

DFS后打表

 1 #include <iostream>
 2 using namespace std;
 3 int s[] ={0,0,0,4,6,0,0,12,40,0,0,171,410,0,0,1896,5160,0,0,32757,59984,0,0,431095,822229};
 4 int main()
 5 {
 6     int n;
 7     while(~scanf("%d",&n)&n)
 8     {
 9         printf("%d %d\n",n,s[n]);
10     }
11 }

 1 #include <iostream>
 2 using namespace std;
 3 int s[25][25];
 4 int a,b;
 5 int n,cnt;
 6 void dfs(int x)
 7 {
 8     if(x==n+1)
 9     {
10         int i,j;
11         a=b=0;
12         for(j=1;j<=n;j++)
13         if(s[1][j]) a++;
14         else b++;
15         for(int i=2;i<=n;i++)
16         {
17             for(j=1;j<=n-i+1;j++)
18             {
19                 if(s[i-1][j]==s[i-1][j+1]) {
20                     s[i][j]=1;
21                     a++;
22                 } else {
23                     s[i][j]=0;
24                     b++;
25                 }
26             }
27         }
28         if(a==b) cnt++;
29         return;
30     }
31     s[1][x]=0;
32     dfs(x+1);
33     s[1][x]=1;
34     dfs(x+1);
35 }
36 int main()
37 {
38     for(n=1;n<=24;n++)
39     {
40         cnt=0;
41         dfs(1);
42         printf("%d,",cnt);
43     }
44 }