Codeforces 263A. Appleman and Easy Task

A. Appleman and Easy TaskTime limit per test 1 secondmemory limit per test megabytes input Standard Input Output Standard Output

Toastman came up and a very easy task. He gives it to Appleman, but Appleman doesn ' t know what to solve it. Can you help him?

Given a n x n Checkerboard. Each cell of the board has either character 'X ', or character 'o '. Is it true this each cell of the board have even number of adjacent cells with 'o '? Both cells of the board are adjacent if they share a side.

Input

The first line contains an integer n (1≤ n ≤100). Then n lines follow containing the description of the checkerboard. Each of them contains n characters (either 'x ' or 'o ') without spaces.

Output

Print "YES" or "NO" (without the quotes) depending on the answer to the problem.

Sample Test (s)Input

3
Xxo
XOX
Oxx

Output

YES

Input

4
Xxxo
xoxo
Oxox
Xxxx

Output

NO

Problem solving: Brute force enumeration.

1#include <iostream>2#include <cstdio>3#include <cstring>4#include <cmath>5#include <algorithm>6#include <climits>7#include <vector>8#include <queue>9#include <cstdlib>Ten#include <string> One#include <Set> A#include <stack> - #defineLL Long Long - #definePII pair<int,int> the #defineINF 0x3f3f3f3f - using namespacestd; - Const intMAXN = the; - intN; + CharMP[MAXN][MAXN]; - Const intdir[4][2] = {0,-1,0,1,-1,0,1,0}; + intMain () { A     intans; at     BOOLFlag; -      while(~SCANF ("%d",&N)) { - GetChar (); -Memset (MP,'x',sizeof(MP)); -          for(inti =1; I <= N; i++){ -              for(intj =1; J <= N; J + +) inMP[I][J] =GetChar (); - GetChar (); to         } +Flag =true; -          for(inti =1; I <= N; i++){ the              for(intj =1; J <= N; J + +){ *Ans =0; $                  for(intK =0; K <4; k++){Panax Notoginseng                     intx = i+dir[k][0]; -                     inty = j+dir[k][1]; the                     if(Mp[x][y] = ='o') ans++; +                 } A                 if(ans&1) {flag =false; Break;} the             } +         } -Flag?puts ("YES"):p UTS ("NO"); $     } $     return 0; -}

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Codeforces 263A. Appleman and Easy Task