Question:what's mean "undefined reference to "

[gongzhen]

None.

[gongzhen]

Forget to add the line for your guys:
The error message line is :
when I call function in main.cpp;
run_simulation(arrival_q, numberCheckers, fout);

[Disch]

It means you never gave that function a body.

[Moschops]

It means you haven't provided the code for the run_simulation function. You've declared the function, but you haven't actually provided the implementation.

[gongzhen]

Thank you guys. I am really fool. I forget that point. thanks.