hzau 1208 Color Circle（dfs）

1208: Color Circle

Time Limit: 1 Sec Memory Limit: 1280 MB
Submit: 289 Solved: 85
[Submit][Status][Web Board]

Description

There are colorful flowers in the parterre in front of the door of college and form many beautiful patterns. Now, you want to find a circle consist of flowers with same color. What should be done ?

Assuming the flowers arranged as matrix in parterre, indicated by a N*M matrix. Every point in the matrix indicates the color of a flower. We use the same uppercase letter to represent the same kind of color. We think a sequence of points d1, d2, … dk makes up a circle while:

1. Every point is different.

2. k >= 4

3. All points belong to the same color.

4. For 1 <= i <= k-1, di is adjacent to di+1 and dk is adjacent to d1. ( Point x is adjacent to Point y while they have the common edge).

N, M <= 50. Judge if there is a circle in the given matrix.

Input

There are multiply test cases.

In each case, the first line are two integers n and m, the 2nd ~ n+1th lines is the given n*m matrix. Input m characters in per line.

Output

Output your answer as “Yes” or ”No” in one line for each case.

Sample Input

3 3
AAA
ABA
AAA

Sample Output

Yes

HINT

dfs

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 
 4 const int MAXN = 55;
 5 
 6 int dir[4][2] = {{-1, 0}, {1, 0}, {0, -1}, {0, 1},};
 7 char g[MAXN][MAXN];
 8 int depth[MAXN][MAXN];
 9 bool vis[MAXN][MAXN];
10 int n, m;
11 char bg;
12 bool circle;
13 
14 void init()
15 {
16     memset(g, '', sizeof(g));
17     memset(depth, 0, sizeof(depth));
18     memset(vis, false, sizeof(vis));
19     circle = false;
20 }
21 
22 bool check(int r, int c)
23 {
24     if (r < 0 || r >= n) {
25         return false;
26     }
27     if (c < 0 || c >= m) {
28         return false;
29     }
30     return true;
31 }
32 
33 void dfs(int r, int c, int d)
34 {
35     if (circle) {
36         return;
37     }
38     int i;
39     int r2, c2;
40     for (i = 0; i < 4; ++i) {
41         r2 = r + dir[i][0];
42         c2 = c + dir[i][1];
43         if (!check(r2, c2)) {//越界
44             continue;
45         }
46         if (g[r][c] != bg) {//不同
47             continue;
48         }
49         if (!vis[r2][c2]) {//没访问过
50             vis[r2][c2] = true;
51             depth[r2][c2] = d + 1;
52             dfs(r2, c2, d + 1);
53             depth[r2][c2] = 0;
54             vis[r2][c2] = false;
55         } else if (d - depth[r2][c2] + 1 >= 4) {//找到环
56             circle = true;
57             return;
58         }
59     }
60 }
61 
62 int main()
63 {
64     int i, j;
65 
66     while (~scanf("%d%d", &n, &m)) {
67         //init();
68         for (i = 0; i < n; ++i) {
69             scanf("%s", g[i]);
70         }
71         circle = false;
72         for (i = 0; i < n; ++i) {
73             for (j = 0; j < m; ++j) {
74                 bg = g[i][j];
75                 vis[i][j] = true;
76                 depth[i][j] = 1;
77                 dfs(i, j, 1);
78                 depth[i][j] = 0;
79                 vis[i][j] = false;
80                 if (circle) {
81                     break;
82                 }
83             }
84             if (circle) {
85                 break;
86             }
87         }
88         if (circle) {
89             printf("Yes
");
90         } else {
91             printf("No
");
92         }
93     }
94 
95     return 0;
96 }