Tree - Depth-First Search (DFS)

Data System Architecture


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.


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


        /  |  \
      /    |   \
    d      e    g
   /|\          |
  / | \         f
 a  b  c

  • pre-order (hdabcegf),
  • post-order (abcdefgh)

Documentation / Reference

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