Amortized Analysis

Formal, also gives us a chance to practice.

• A credit buys: one call to VISIT.
• Credit rule: Every white node has one coin for each of its outgoing edges.
• Charge for operation: n+m for TOPOLOGICAL-SORT.
• Accounting: We do n work making all nodes white, and then ``place'' credits on each node u. Note that the total credits we put down in the main routine is

  

  In , we turn u gray, ``freeing'' credits, which we spend on the loop over adjacent nodes.