DFS Codeforces Round #290 (Div. 2) B. Fox And Two Dots

 

题目传送门

 1 /*  2  DFS：每个点四处寻找，判断是否与前面的颜色相同，当走到已走过的表示成一个环  3 */  4 #include <cstdio>  5 #include <iostream>  6 #include <cstring>  7 #include <string>  8 #include <map>  9 #include <algorithm> 10 #include <vector> 11 #include <set> 12 #include <cmath> 13 using namespace std; 14 15 const int MAXN = 1e6 + 10; 16 const int INF = 0x3f3f3f3f; 17 int dx[4] = {1, -1, 0, 0}; 18 int dy[4] = {0, 0, 1, -1}; 19 char a[55][55]; 20 int used[55][55]; 21 int n, m; 22 23 bool DFS(int x, int y, int px, int py, char ch) 24 { 25 used[x][y] = 1; 26 for (int i=0; i<=4-1; ++i) 27  { 28 int tx = x + dx[i]; 29 int ty = y + dy[i]; 30 if (tx == px && ty == py) continue; 31 if (tx >= 0 && tx <= n-1 && ty >= 0 && ty <=m-1 && a[tx][ty] == ch) 32  { 33 if (used[tx][ty]) return true; 34 if (DFS (tx, ty, x, y, ch)) return true; 35  } 36  } 37 38 return false; 39 } 40 41 int main(void) 42 { 43 //freopen ("B.in", "r", stdin); 44 45 while (cin >> n >> m) 46  { 47 memset (used, 0, sizeof (used)); 48 for (int i=0; i<=n-1; ++i) 49  { 50 scanf ("%s", &a[i]); 51  } 52 53 bool flag = false; 54 for (int i=0; i<=n-1; ++i) 55  { 56 for (int j=0; j<=m-1; ++j) 57  { 58 if (!used[i][j]) 59  { 60 if (DFS (i, j, -1, -1, a[i][j])) 61  { 62 puts ("Yes"); flag = true; break; 63  } 64  } 65  } 66 if (flag) break; 67  } 68 69 if (!flag) puts ("No"); 70  } 71 72 return 0; 73 }