View Compilation Error

0_0_22704029_7262.cpp:3:26: error: array bound is not an integer constant before ']' token
 int T,n,k,u,v,ans,sz[maxn];
                          ^
0_0_22704029_7262.cpp:4:1: error: 'vector' does not name a type
 vector<int>G[maxn];
 ^
0_0_22704029_7262.cpp: In function 'void dfs(int, int)':
0_0_22704029_7262.cpp:6:5: error: 'sz' was not declared in this scope
     sz[u]=1;
     ^
0_0_22704029_7262.cpp:7:18: error: 'G' was not declared in this scope
     for (auto& v:G[u]){
                  ^
0_0_22704029_7262.cpp: In function 'int main()':
0_0_22704029_7262.cpp:15:16: error: 'read' was not declared in this scope
     for (read(T);T--;){
                ^
0_0_22704029_7262.cpp:17:32: error: 'sz' was not declared in this scope
         for (int i=1;i<=n;i++) sz[i]=0,G[i].clear();
                                ^
0_0_22704029_7262.cpp:17:40: error: 'G' was not declared in this scope
         for (int i=1;i<=n;i++) sz[i]=0,G[i].clear();
                                        ^
0_0_22704029_7262.cpp:20:13: error: 'G' was not declared in this scope
             G[u].push_back(v);
             ^