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.
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 your answer as “Yes” or ”No” in one line for each case.
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, ‘\0‘, 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\n");
90 } else {
91 printf("No\n");
92 }
93 }
94
95 return 0;
96 }
