hzau 1208 Color Circle（dfs）

1208: Color Circle

Time Limit: 1 Sec  Memory Limit: 1280 MB
Submit: 289  Solved: 85
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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

 #include <bits/stdc++.h>
 using namespace std;

 const int MAXN = ;

 int dir[][] = {{-, }, {, }, {, -}, {, },};
 char g[MAXN][MAXN];
 int depth[MAXN][MAXN];
 bool vis[MAXN][MAXN];
 int n, m;
 char bg;
 bool circle;

 void init()
 {
     memset(g, '\0', sizeof(g));
     memset(depth, , sizeof(depth));
     memset(vis, false, sizeof(vis));
     circle = false;
 }

 bool check(int r, int c)
 {
     if (r <  || r >= n) {
         return false;
     }
     if (c <  || c >= m) {
         return false;
     }
     return true;
 }

 void dfs(int r, int c, int d)
 {
     if (circle) {
         return;
     }
     int i;
     int r2, c2;
     for (i = ; i < ; ++i) {
         r2 = r + dir[i][];
         c2 = c + dir[i][];
         if (!check(r2, c2)) {//越界
             continue;
         }
         if (g[r][c] != bg) {//不同
             continue;
         }
         if (!vis[r2][c2]) {//没访问过
             vis[r2][c2] = true;
             depth[r2][c2] = d + ;
             dfs(r2, c2, d + );
             depth[r2][c2] = ;
             vis[r2][c2] = false;
         } else if (d - depth[r2][c2] +  >= ) {//找到环
             circle = true;
             return;
         }
     }
 }

 int main()
 {
     int i, j;

     while (~scanf("%d%d", &n, &m)) {
         //init();
         for (i = ; i < n; ++i) {
             scanf("%s", g[i]);
         }
         circle = false;
         for (i = ; i < n; ++i) {
             for (j = ; j < m; ++j) {
                 bg = g[i][j];
                 vis[i][j] = true;
                 depth[i][j] = ;
                 dfs(i, j, );
                 depth[i][j] = ;
                 vis[i][j] = false;
                 if (circle) {
                     break;
                 }
             }
             if (circle) {
                 break;
             }
         }
         if (circle) {
             printf("Yes\n");
         } else {
             printf("No\n");
         }
     }

     return ;
 }