prepare (1/3): 
finished

make (2/3): 
clang -std=gnu11 -O2 -Wall  -o main main.c
main.c:96:10: warning: unused variable 'root' [-Wunused-variable]
    int *root = malloc(sizeof(int)*edge_num);
         ^
1 warning generated.
main successfully constructed
finished

clean (3/3): 
finished

all task finished, build successfully