About
Depth-First Search is a tree traversal in a depth-frist order. ie The search tree is deepened as much as possible on each child before going to the next sibling.
Algorithm
At node N, in any order:
- (L) Recursively traverse its left subtree. When this step is finished you are back at N again.
- (R) Recursively traverse its right subtree. When this step is finished you are back at N again.
- (N) Process N itself.
| Traversal Type | Condition |
|---|---|
| left-to-right | If (L) is done before (R) |
| right-to-left | If (R) is done before (L) |
Left-To-Right Algorithm
The order prefix (ie pre in pre-order) refers to the display position of the root or current node.
| Order | display the root or current node (…) the left or right branch of the tree |
|---|---|
| pre-order | before |
| in-order | between (only for binary tree) |
| post-order | after |
Example
h
/ | \
/ | \
d e g
/|\ |
/ | \ f
a b c
- pre-order (hdabcegf),
- post-order (abcdefgh)