View Compilation Error

0_0_22232449_13079.cpp: In function 'int solve(int, int, int)':
0_0_22232449_13079.cpp:8:8: error: 'vis' was not declared in this scope
     if(vis[l][pre][now]) return dp[l][pre][now];
        ^
0_0_22232449_13079.cpp:9:5: error: 'vis' was not declared in this scope
     vis[l][pre][now] = true;
     ^