NIST

level-order traversal

(algorithm)

Definition: Process all nodes of a tree by depth: first the root, then the children of the root, etc. Equivalent to a breadth-first search from the root.

See also postorder traversal, preorder traversal, tree traversal, Cupif-Giannini tree traversal, level (1).

Note: For instance, if the "processing" is just printing, a tree is printed as "root, all children of the root, all grandchildren (children of children) of the root, etc." Here is pseudocode for an inefficient level-order traversal of a binary tree:

 levelorderAux(tree, level)
begin
if tree is null, return;

if level is 1, then
print(tree.root);
else if level greater than 1, then
levelorderAux(tree.left_subtree, level-1);
levelorderAux(tree.right_subtree, level-1);
endif
end

levelorder(tree)
begin
for d = 1 to height(tree)
levelorderAux(tree, d);
endfor
end

See [Stand98, p. 251].

Author: PEB


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Entry modified 10 February 2017.
HTML page formatted Fri Feb 23 10:06:08 2018.

Cite this as:
Paul E. Black, "level-order traversal", in Dictionary of Algorithms and Data Structures [online], Vreda Pieterse and Paul E. Black, eds. 10 February 2017. (accessed TODAY) Available from: https://www.nist.gov/dads/HTML/levelOrderTraversal.html