prepare (1/3): 
finished

make (2/3): 
g++ -std=c++11 -Wall -o main main.cpp 
main.cpp: In function 'bool check_mst(std::vector<node*>)':
main.cpp:64:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i< T.size(); i++) {
                  ~^~~~~~~~~~
main.cpp: In function 'int main()':
main.cpp:149:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if(T.size()!=N||!check_mst(T)) cout<<"No MST exists!"<<endl;
     ~~~~~~~~^~~
finished

clean (3/3): 
finished

all task finished, build successfully