prepare (1/3): 
finished

make (2/3): 
g++ -g -Wall -O2 -c lab3.cpp
lab3.cpp: In function 'int main(int, char* const*)':
lab3.cpp:70:37: warning: 'PQ' may be used uninitialized in this function [-Wmaybe-uninitialized]
  priority_queue<grid_t, compare_t> *PQ;
                                     ^~
g++ -g -Wall -O2 -o main lab3.o
finished

clean (3/3): 
finished

all task finished, build successfully