View Compilation Error

0_0_30280688_32505.cpp: In function 'bool dfs(int, int, int, int)':
0_0_30280688_32505.cpp:8:5: error: 'vis' was not declared in this scope
     vis[u/4+1][u%4==0?4:u%4]++;
     ^
0_0_30280688_32505.cpp: In function 'int main()':
0_0_30280688_32505.cpp:35:21: error: 'vis' was not declared in this scope
                 if(!vis[i][j]&&a[i][j]&&a[i][j]!=(i-1)*4+j)
                     ^