prepare (1/3): 
finished

make (2/3): 
g++ -g -Wall -O2 -std=c++11 -o main.o -c main.cpp 
main.cpp: In constructor 'graph_t::graph_t(unsigned int)':
main.cpp:62:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (int i = 0; i < num; i++)
                             ~~^~~~~
g++ -g -Wall -O2 -std=c++11 -o main  main.o
finished

clean (3/3): 
finished

all task finished, build successfully