B. Fox And Two Dots( Codeforces Round #290 (Div. 2))
2015-02-03 14:12
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B. Fox And Two Dots
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output
Fox Ciel is playing a mobile puzzle game called "Two Dots". The basic levels are played on a board of size n × m cells, like this:
![](http://espresso.codeforces.com/56dcae7c8d1ee32ea083e76eb5cd70ae21b63c24.png)
Each cell contains a dot that has some color. We will use different uppercase Latin characters to express different colors.
The key of this game is to find a cycle that contain dots of same color. Consider 4 blue dots on the picture forming a circle as an example. Formally, we call a sequence of dots d1, d2, ..., dk a cycle if
and only if it meets the following condition:
These k dots are different: if i ≠ j then di is
different from dj.
k is at least 4.
All dots belong to the same color.
For all 1 ≤ i ≤ k - 1: di and di + 1 are
adjacent. Also, dk and d1 should
also be adjacent. Cells x and y are called adjacent
if they share an edge.
Determine if there exists a cycle on the field.
Input
The first line contains two integers n and m (2 ≤ n, m ≤ 50):
the number of rows and columns of the board.
Then n lines follow, each line contains a string consisting of m characters,
expressing colors of dots in each line. Each character is an uppercase Latin letter.
Output
Output "Yes" if there exists a cycle, and "No"
otherwise.
Sample test(s)
input
output
input
output
input
output
input
output
input
output
Note
In first sample test all 'A' form a cycle.
In second sample there is no such cycle.
The third sample is displayed on the picture above ('Y' = Yellow, 'B'
= Blue, 'R' = Red).
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output
Fox Ciel is playing a mobile puzzle game called "Two Dots". The basic levels are played on a board of size n × m cells, like this:
![](http://espresso.codeforces.com/56dcae7c8d1ee32ea083e76eb5cd70ae21b63c24.png)
Each cell contains a dot that has some color. We will use different uppercase Latin characters to express different colors.
The key of this game is to find a cycle that contain dots of same color. Consider 4 blue dots on the picture forming a circle as an example. Formally, we call a sequence of dots d1, d2, ..., dk a cycle if
and only if it meets the following condition:
These k dots are different: if i ≠ j then di is
different from dj.
k is at least 4.
All dots belong to the same color.
For all 1 ≤ i ≤ k - 1: di and di + 1 are
adjacent. Also, dk and d1 should
also be adjacent. Cells x and y are called adjacent
if they share an edge.
Determine if there exists a cycle on the field.
Input
The first line contains two integers n and m (2 ≤ n, m ≤ 50):
the number of rows and columns of the board.
Then n lines follow, each line contains a string consisting of m characters,
expressing colors of dots in each line. Each character is an uppercase Latin letter.
Output
Output "Yes" if there exists a cycle, and "No"
otherwise.
Sample test(s)
input
3 4 AAAA ABCA AAAA
output
Yes
input
3 4 AAAA ABCA AADA
output
No
input
4 4 YYYR BYBY BBBY BBBY
output
Yes
input
7 6 AAAAAB ABBBAB ABAAAB ABABBB ABAAAB ABBBAB AAAAAB
output
Yes
input
2 13 ABCDEFGHIJKLM NOPQRSTUVWXYZ
output
No
Note
In first sample test all 'A' form a cycle.
In second sample there is no such cycle.
The third sample is displayed on the picture above ('Y' = Yellow, 'B'
= Blue, 'R' = Red).
#include<iostream> #include<algorithm> #include<stdio.h> #include<string.h> #include<stdlib.h> #include<queue> using namespace std; int n,m; char map[51][51]; int v[51][51]; int jx[] = {0,1,0,-1}; int jy[] = {1,0,-1,0}; int flag = 0; struct node { int x; int y; }; void DFS(int xx,int yy,int x1,int y1) { for(int i=0; i<4; i++) { if(flag == 1) { return ; } int x,y; x = xx + jx[i]; y = yy + jy[i]; if(v[x][y] == 1 && map[xx][yy] == map[x][y] && x1!=x && y1!=y && x>=0 && x<n && y>=0 && y<m) { printf("Yes\n"); flag = 1; return ; } if(v[x][y] == 0) { if(map[xx][yy] == map[x][y] && x>=0 && x<n && y>=0 && y<m) { //printf("x = %d y = %d\n",x,y); v[x][y] = 1; DFS(x,y,xx,yy); } } } } int main() { while(scanf("%d%d",&n,&m)!=EOF) { flag = 0; memset(v,0,sizeof(v)); for(int i=0; i<n; i++) { scanf("%s",map[i]); } for(int i=0; i<n; i++) { for(int j=0; j<m; j++) { if(v[i][j] == 0 && flag == 0) { DFS(i,j,i,j); } } } if(flag == 0) { printf("No\n"); } } return 0; }
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