# Questions tagged [traversal]

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5 votes
2 answers
155 views

### How to mark leaves of polynomial based on its position in tree

I've been struggling with this for a few days, and so I thought I might ask this here. Part of the problem lies in the fact that I do not even know the mathematical solution, which runs the risk of ...
• 19.5k
9 votes
1 answer
431 views

### How to perform a depth-first in-order traversal of an expression?

To complement my earlier questions: How to perform a breadth-first traversal of an expression? How to perform a depth-first preorder traversal of an expression? I would now like to ask: how to ...
• 270k
5 votes
3 answers
356 views

### a function to extract all subexpressions from an expression

Can somebody help me with a function f such that it extract all sub expressions (i.e. looking down the expression tree) from any expression given to it and also a ...
• 9,113
5 votes
1 answer
218 views

### How to make a postordered ReplaceAll that operates just once per subtree?

The answers to this question provide code for a function I'll call postOrderReplaceAll to replace from the inside-out: ...
• 434
3 votes
1 answer
214 views

### why Level does not sort output according to their levels

Consider this example: Level[a + f[x, y^n], {0, Infinity}] (*{a, x, y, n, y^n, f[x, y^n], a + f[x, y^n]}*) Why the output is sorted in this way. why not ...
• 19.7k
3 votes
5 answers
470 views

### Take the next element in a nested list

My problem is the following: Consider a list of elements. To better understanding my following explanations, I would take this example: ...
• 616
4 votes
1 answer
308 views

### Forcing optimal solution for FindShortestTour

I use FindShortestTour as explained here and it works nicely for a small number of cities. However when I try this with as little as 16 cities, the given tour isn't ...
• 141
12 votes
1 answer
428 views

### Position with Except returns first item {0} and last item {}. Why?

Here is a simple list: l={1, 0, 2, 1, 0, 1, 0, 1, 2, 0, 2, 0, 1, 0, 1, 0, 0} To get the position of non-zero elements I use ...
• 547
16 votes
2 answers
2k views

### Visiting nodes in a tree bottom up

I have a problem that can be reduced to this one: Suppose I have an unbalanced (almost random) tree. The leaves of the tree have one property already set, and all vertex (including the leaves) have ...
• 115k
33 votes
5 answers
2k views

### How to perform a depth-first preorder traversal of an expression?

Mathematica provides functions that perform a depth-first postorder traversal, or which use such a traversal, including: Scan, ...
• 270k
28 votes
7 answers
2k views

### How to perform a breadth-first traversal of an expression?

Mathematica provides functions that perform a depth-first traversal, or which use such a traversal, including: Scan, Count, <...
• 270k
14 votes
3 answers
752 views

### Determining all possible traversals of a tree

I have a list: B={423, {{53, {39, 65, 423}}, {66, {67, 81, 423}}, {424, {25, 40, 423}}}}; This list can be visualized as a tree using ...
• 10.4k