Hello codeforces ,

i'm brand new to dfs and i have spend like 4 hours trying to find a solution for The Tag Game problem.

what i have tried:

bob wants to maxmizes the solution , alice wants to minimize , so bob need to reach the deepest node , when bob reaches it alice will move to catch him , but bob has the choice to stay in the node (each of them has that option but i guess only bob will use it) i can't handle this choice of staying as a move, this is my code:

const int N_=10e5+6,M=2*10e5+6;
const int NOT_VISITED = 0 , IN_PROGRESS = 1 , VISITED = 2;
int m,n,u,v;
vector<int> adj[N_];
vector<pair<int,int>> dxdy = {{-1,0},{1,0},{0,1},{0,-1}};
// vector<vector<bool>> vis;
bool vis[N_];
int c;

// bool isValid(int x , int y , vector<STR>&grid){
//    if(x < 0 || x > n-1 || y <0 || y>m-1) return false;
//    if(vis[x][y] || grid[x][y] == '#') return false;
//    return true;
// }
int md = 0 , fn=0;
void dfs(int u,int depth){
   vis[u] =true;
   if(depth > md){
      md = depth;
      fn = u;
   }
   c++;
   for(auto x : adj[u]){
      if(!vis[x]){
         dfs(x,depth+1);
      }
   }
}

void solve()
{
   cin >> n>>m;
   for(int x = 0 ;x < n-1 ; x++){
      cin >>u >>v;
      adj[u].push_back(v);
      adj[v].push_back(u);
   }
   dfs(m,0);
   int ans = md;
   memset(vis,false,sizeof(vis));
   md=0;
   c=0;
   dfs(1,0);
   c-=2;
   cout << ans+c+md;
   
}