Backward algorithm
Wednesday, December 02, 2009
11:24 AM
Backward scan: 
Mark end's latest start time and latest completion time as its earliest start time and completion time. 
From right to left (finish to start), 
If a task's successors are marked with latest start time, 
its latest completion time is the minimum of successor latest start times and 
its latest start time is its latest completion time minus its duration. 
At the end, every node is labeled with its latest start and completion times. 