Rollup merge of #93606 - JakobDegen:mischaracterized-preorder, r=oli-obk

Correct incorrect description of preorder traversals

The internal documentation for the `Preorder` type gave an incorrect description (the description is not even correct for the example provided, since C is visited after one of its successors). This corrects the description, and adds in a sentence explaining more precisely how the traversals are performed.
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Yuki Okushi 2022-02-03 22:20:29 +09:00 committed by GitHub
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@ -4,8 +4,9 @@
/// Preorder traversal of a graph.
///
/// Preorder traversal is when each node is visited before any of its
/// successors
/// Preorder traversal is when each node is visited after at least one of its predecessors. If you
/// are familar with some basic graph theory, then this performs a depth first search and returns
/// nodes in order of discovery time.
///
/// ```text
///
@ -82,8 +83,9 @@ fn size_hint(&self) -> (usize, Option<usize>) {
/// Postorder traversal of a graph.
///
/// Postorder traversal is when each node is visited after all of its
/// successors, except when the successor is only reachable by a back-edge
/// Postorder traversal is when each node is visited after all of its successors, except when the
/// successor is only reachable by a back-edge. If you are familiar with some basic graph theory,
/// then this performs a depth first search and returns nodes in order of completion time.
///
///
/// ```text