CodeForces Round #290 Div.2

 1 #include <cstdio>
 2 
 3 int main()
 4 {
 5     //freopen("in.txt", "r", stdin);
 6 
 7     int n, m;
 8     scanf("%d%d", &n, &m);
 9     for(int i = 1; i <= n; ++i)
10     {
11         if(i % 4 == 1 || i % 4 == 3) for(int j = 0; j < m; ++j) printf("#");
12         else if(i % 4 == 2)
13         {
14             for(int j = 1; j < m; ++j) printf(".");
15             printf("#");
16         }
17         else
18         {
19             printf("#");
20             for(int j = 1; j < m; ++j) printf(".");
21         }
22         printf("\n");
23     }
24 
25     return 0;
26 }

 1 #include <cstdio>
 2 
 3 const int maxn = 50 + 5;
 4 int n, m;
 5 int vis[maxn][maxn];
 6 char map[maxn][maxn];
 7 int dx[] = {0, 1, 0, -1};
 8 int dy[] = {1, 0, -1, 0};
 9 
10 bool dfs(int x, int y, int d, char color)
11 {
12     vis[x][y] = d;
13     for(int i = 0; i < 4; ++i)
14     {
15         int xx = x + dx[i];
16         int yy = y + dy[i];
17         if(xx>=0&&xx<n&&yy>=0&&yy<m && map[xx][yy] == color)
18         {
19             if(vis[xx][yy] && vis[x][y] - vis[xx][yy] > 1) return true;
20             else if(!vis[xx][yy])
21                 //return dfs(xx, yy, d+1, color);
22                 if(dfs(xx, yy, d+1, color)) return true;
23         }
24     }
25     return false;
26 }
27 
28 int main()
29 {
30     //freopen("in.txt", "r", stdin);
31 
32     scanf("%d%d", &n, &m);
33     for(int i = 0; i < n; ++i)
34         scanf("%s", map[i]);
35 
36     for(int i = 0; i < n; ++i)
37         for(int j = 0; j < m; ++j) if(!vis[i][j])
38             if(dfs(i, j, 1, map[i][j]))
39             {
40                 printf("Yes\n");
41                 return 0;
42             }
43 
44     printf("No\n");
45 
46     return 0;
47 }

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 
 5 const int maxn = 100 + 10;
 6 int n, len[maxn], t, c[maxn];
 7 char names[maxn][maxn], ans[30];
 8 bool G[26][26];
 9 
10 bool dfs(int u)
11 {
12     c[u] = -1;
13     for(int v = 0; v < 26; ++v) if(G[u][v])
14     {
15         if(c[v] < 0) return false;
16         else if(!c[v] && !dfs(v)) return false;
17     }
18     c[u] = 1; ans[--t] = u + ‘a‘;
19     return true;
20 }
21 
22 bool topo()
23 {
24     t = 26;
25     memset(c, 0, sizeof(c));
26     for(int u = 0; u < 26; ++u) if(!c[u]) if(!dfs(u)) return false;
27     return true;
28 }
29 
30 int main()
31 {
32     //freopen("in.txt", "r", stdin);
33 
34     scanf("%d", &n);
35     for(int i = 0; i < n; ++i) { scanf("%s", names[i]); len[i] = strlen(names[i]); }
36     for(int i = 0; i < n; ++i)
37     {
38         int l1 = len[i];
39         for(int j = i+1; j < n; ++j)
40         {
41             int l2 = len[j];
42             int p = 0;
43             while(names[i][p] == names[j][p] && p < l1 && p < l2) p++;
44             if(p == l1) continue;
45             else if(p == l2)
46             {//bbba无论怎样都不会比bb字典序小
47                 puts("Impossible");
48                 return 0;
49             }
50             else
51             {
52                 char c1 = names[i][p], c2 = names[j][p];
53                 G[c1-‘a‘][c2-‘a‘] = true;
54             }
55         }
56     }
57 
58     if(topo()) printf("%s\n", ans);
59     else puts("Impossible");
60 
61     return 0;
62 }