Method TraverseDepthFirst

TraverseDepthFirst<T>(T, Func<T, IEnumerable<T>>)

Traverses a tree in a depth-first fashion, starting at a root node and using a user-defined function to get the children at each node of the tree.

Declaration

public static IEnumerable<T> TraverseDepthFirst<T>(T root, Func<T, IEnumerable<T>> childrenSelector)

Parameters

Type	Name	Description
T	root	The root of the tree to traverse.
Func<T, IEnumerable<T>>	childrenSelector	The function that produces the children of each element.

Returns

Type	Description
IEnumerable<T>	A sequence containing the traversed values.

Type Parameters

Name	Description
T	The tree node type.

Remarks

The tree is not checked for loops. If the resulting sequence needs to be finite then it is the responsibility of childrenSelector to ensure that loops are not produced.

This function defers traversal until needed and streams the results.

Examples

The following code example demonstrates how to traverse a tree depth-first using TraverseDepthFirst.

Node root = new(0,
[
    new(1), new(2), new(3),
    new(4,
    [
        new(5), new(6),
        new(7, [ new(8), new(9) ]),
        new(10, [ new(11) ]),
    ]),
    new(11),
    new(12,
    [
        new(13), new(14),
        new(15, [ new(16), new(17) ]),
        new(18),
    ]),
    new(19), new(20),
]);

// Traverse a tree
var result = SuperEnumerable
    .TraverseDepthFirst(
        root,
        static x => x.Children ?? [])
    .Select(x => x.Id);

Console.WriteLine(
    "[" +
    string.Join(", ", result) +
    "]");

// This code produces the following output:
// [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

record Node(int Id, IEnumerable<Node>? Children = null);

Exceptions

Type	Condition
ArgumentNullException	childrenSelector is null.