prepare (1/3): 
finished

make (2/3): 
g++ -Wall -std=c++11 -O2 -o main main.cpp
main.cpp: In function 'int main(int, const char**)':
main.cpp:108:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if (seen_node.size() != node_number) std::cout << "The graph is not a DAG" << std::endl;
         ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
main.cpp:189:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if (MST_nodes.size() != node_number) {
         ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
finished

clean (3/3): 
finished

all task finished, build successfully