complete constriant 1&2 (e.g. source & destination = 1)
complete obj function (Xij)
Merge branch 'master' into obj

Conflicts:
	hw1.c
Merge branch 'obj' into const

Conflicts:
	hw1.c
complete node1's  flow conservation law formula
complete all formula , hope it work.
add void in main()'s ()

remove unsed integer k

fix bugs by const1 & const2
fix bugs by other constraints

I probably complete optimizing a simple topology
finally complete big topolopy, but it's a stupid version.
test it now!