Homework 4
			due Thurs. at 5 p.m., Feb.. 24
			(Please hand in under my office door, 336 WVH.
			 If this is a burden, then please mail this
			 assignment (scan of handwritten or other format)
			 directly to the grader.  His e-mail is:
			 ( first four letters:  chen
			   next two letters, appended:  yr
			   and then append:  @ccs.neu.edu )
			(hardcopy only, handwritten is fine)

Please note that I am setting a deadline of next Thursday so that
the grader will still have time to grade them before the mid-term.
I will arrange later times to pick up the homeworks.  This unusual
arrangement is forced on us because Mon., Feb. 21 is a university holiday
and Mon., Feb. 28 is Spring break.

These exercises are from Chapters 4 and 5.  Exercises:
  4.13,, 4.14, 4.16 (binary heap as priority queue), 4.20, 4.22
  5.1, 5.4, 5.5, 5.6, 5.9 (except part (i) on Prim's algo.), 5.10,
  5.20, 5.23, 5.24

Note:  Dijkstra's algorithm analyzes graphs with positive weights.  Only
  the Bellman-Ford algorithm of the chapter (not discussed in class)
  handles general graphs with negative weights.  Ex. 4.9 asks to analyze
  Dijkstra's algorithm for a very special graph with some negative graphs.