For questions about trees in graph theory, which are connected graphs with no cycles. Also can be used for questions about forests, which are graphs that are disjoint unions of trees.

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Binary Heap Question interpretation

In the question in the link below, how do I tell weather to draw out a binary min heap or a binary max heap? Am I misunderstanding the question? Binary Heap Question
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1answer
64 views

How to generate (recursively?) all non-isomorphic trees with 2 types of vertex labels with degree restrictions?

I am not sure if the title makes a whole lot of sense, but what I am trying to do is generate all non-isomorphic trees that obey the following: 1) Each vertex (including leaves) has one of two labels ...
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1answer
20 views

What is the maximum number of “root subtrees” that a tree can have?

Let $T=(V,E)$ be a directed rooted tree with root $r \in V$. A root subtree$^1$ of $T$ is a directed rooted tree $T'=(V',E')$ that fulfills the following conditions: $T'$ is a subgraph of $T$, $r \...
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1answer
30 views

Fundamental group of cylinder -triangulation method

Is this correct? Can we conclude that the fundamental group is trivial since there are no remaining generators on 1-simplices?
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23 views

Fundamental group Klein Bottle triangulation

I have been trying to find the FG of the Klein bottle, and I was wondering if someone could verify that this process is correct. After triangulating it, I then found a maximal tree (shown in yellow) ...
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1answer
39 views

Fundamental group of the sphere via triangulation

I know that the fundamental group of the sphere is zero, i.e. $\pi(S^2)=0$ I want to show this by triangulation, i.e: Triangulate the sphere Draw maximal tree Draw maximal contractable subspace ...
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1answer
42 views

Fundamental group of a tree?

Find the fundamental group of the space $C(T)=\{(x,y) \in T \times T \mid x\neq y\}$. $C(T)=\{(x,y) \in T \times T \mid x\neq y\}$ where $T$ is a graph $T$ is the graph made of $3$ edges with a ...
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0answers
255 views

Number of Spanning Arborescences

I am trying to prove the following result from my book: Let $G$ be a directed graph with vertices $x_1,x_2,\dotsc, x_n$ for which a directed Eulerian circuit exists. A spanning arborescence ...
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1answer
33 views

Best way to find if a subgraph has a cycle

I am implementing Kruskal's algorithm to find a minimal spanning tree of a connected graph $G$. If $H$ is a subtree of $G$, does anyone know a smart way of checking if $H+e$, where $e$ is an edge of $...
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0answers
11 views

Minimum spanning trees

Let $G = (V,E)$ be an directed connected graph with $|E|>1$, $w:E→R$ be an edge-weight function and $k∈{1,2,...,|E|-1}$. Sort the edge in E as $e_1,e_2,...,e_|E|$, such that $w(e_1) \leq w(e_2) \...
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5answers
76 views

Prove by induction: A tree on n≥2 vertices has ≥2 leaves

This is what I have. I'm pretty sure this is quite incorrect, but am I at least headed in the right direction? Base Case: $P(2)$: Tree on 2 vertices can only have one edge, the edge connecting the ...
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2answers
47 views

How to efficiently create balanced KD-Trees from a static set of points

From Wikipedia, KD-Trees: Alternative algorithms for building a balanced k-d tree presort the data prior to building the tree. They then maintain the order of the presort during tree construction ...
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1answer
424 views

What is the difference between a forest and a spanning forest?

If a graph is labelled as a forest it does not contain any cycles, meaning it consists of all trees, which I realize can even be a single node (since that is technically a tree). If a graph is ...
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2answers
137 views

Maps of primitive vectors and Conway's river, has anyone built this in SAGE?

I am attempting to teach number theory from John Stillwell's Elements of Number Theory in the upcoming semester. There are two sections (5.7 and 5.8) which describe the diagrammatic method for the ...
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0answers
26 views

Is the path from u to v is diameter of the tree?

The diameter of a tree is the longest (simple) path in the tree. Let u be a vertex in a tree and let v be the farthest from u vertex in T. Show that the path from u to v may not be a diameter I am ...
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0answers
18 views

Minimal spanning trees in multigraphs with constraints

I have a multigraph G whose edges have three identities. Let's say I have three colors of the edges red, blue and green and each two nodes may be connected by a red, blue and/or green edges. The graph ...
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1answer
32 views

Is there an efficient algorithm to find all the maximum matching in any tree?

A matching in a graph (G) is a set of mutually non-adjacent edges of (G). A maximum matching is a matching maxima cardinallity. A tree is an acyclic connected graph. Is there an efficient algorithm ...
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3answers
298 views

Rooted Tree and Greedy Algorithms

In a Rooted Tree, we have a message on Root. in each step, each node that has a one copy of message, can transfer this message to at most one of it's childeren. we want to use minimum step and send ...
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0answers
12 views

Minimum number of pages in a B-Tree of order n?

How can I calculate the minimum number of pages in a B tree of order n and height 3? 1st level = 1 page 2nd level = 2n+1 pages 3rd level = ? 3rd level is 1? Or how many pages?
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1answer
19 views

Completion of acyclic sub graph

Statement: Given an acyclic subgraph of a connected graph, show that this subgraph can be completed into a spanning tree of the graph. I know that there is a theorem that states that any connected ...
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2answers
69 views

Difference between Depth first search and Breadth first search algorithm

Currently I am studying Depth first search algorithm and Breadth first search algorithm. Both these algorithms are looking quite similar to me except for some differences. In BFS, we start with a ...
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0answers
14 views

Minimum Path Cover in Trees

We have a Tree with $m$ nodes and $m-1$ edges. We are given $Q$ queries. Each query consists of a list of nodes of size $k$, $[n_1, n_2, ..., n_k]$. I need to answer the minimum number of paths that ...
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0answers
23 views

Nodes lying on Same Path in Trees

Given a Treen with $n$ nodes and $n-1$ edges, I have to answer $Q$ queries. In every query, I get a list of nodes of size $k$, $n_1, n_2, ..., n_k$. I need to answer the minimum number of paths that ...
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2answers
906 views

Is the graceful labeling conjecture still unsolved?

From the Wikipedia article on graceful labeling: ... A major unproven conjecture in graph theory is the Ringel–Kotzig conjecture, named after Gerhard Ringel and Anton Kotzig, which hypothesizes that ...
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1answer
21 views

Binary Decision Trees

I know the basics to a binary decision tree, but this problem has me a little stumped, and I'm looking for some verification on my ideas. The problem is: "Create a binary decision tree that reflects ...
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1answer
34 views

Constructing a computably infinite tree with no computable infinite branches using PA

Define an infinite tree as any set of sequences closed under prefix restriction, i.e. any prefix restriction of a sequence in the set is also in the set, where a prefix restriction is a restritcion of ...
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1answer
30 views

Show that in a binary tree, if B is the number of branch points (including the root) and L is the number of leaves, then one has the relation L = 1+B

We have been discussing trees lately, but have yet to even touch on the topic of a binary tree. I understand what a leaf is, but we didn't have one for the term "branch points" Without being 100% sure ...
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1answer
52 views

How to prove that each edge of tree is a bridge?

How to prove that each edge of tree is a bridge? My attempt: Tree is a connected graph which has no cycle, and in a connected graph, bridge is a edge whose removal disconnects the graph. Let G ...
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1answer
28 views

Question about theorem with trees

I know the theorem: for an undirected graph on $n$ nodes, any of the following two imply the third: $G$ is connected $G$ does not contain a cycle $G$ has $n-1$ edges (source) ...
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0answers
22 views

Minimum biconnected graph from spanning tree algorithm

I'm thinking about if there exist an algorithm, which can build a biconnected graph from spanning tree? The problem is that it should be minimal-weight (each edge between every pair of nodes has it ...
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1answer
43 views

Minimum spanning tree of graph? proof by contradiction?

this is not a homework but I need to understand it before my exam tomorrow. How to prove by contradiction that a minimum spanning tree of a graph G is unique if all the edge weights in G are distinct?...
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1answer
44 views

Finding the probability using a tree.

Let's say a specific exam has 3 levels (I, II, III). The candidates who pass the first exam are then eligible to take the next level of the exam. Let's say the pass rates for levels I, II, and III are ...
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1answer
16 views

Treewidth Of Graphs And Chordal Completion

https://en.wikipedia.org/wiki/Treewidth The above page explains what a tree decomposition is, and states that treewidth of G is equal to the minimum clique number, minus one, of a chordal ...
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2answers
32 views

You can always delete a vertex from a tree $G$ such that the remaining connected components have size at most $|V(G)|/2$.

I want to prove the statement in the title: for any tree on $n$ vertices, it is possible to delete a vertex such that the deletion leaves connected components with at most $n/2$ vertices each. I drew ...
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0answers
16 views

Finding Height, Number of Leaves, and Value at of Each Node on Recursive Trees

I have an exam tomorrow and am struggling to understand how to get the height of a tree, the number of leaves, and the value of each node. The image is a practice exam. Any tips and help on the first ...
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0answers
19 views

Domain of Injectivity of Analytic Map

Suppose we have an analytic map $f: \mathbb{D} \to \mathbb{C}$. Then the set of points where the function is not locally injective is a discrete set. Suppose first for simplicity that the points ...
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2answers
43 views

Proving the number of leaves of a tree. (Graph Theory)

Prove that if a tree has $n$ vertices (Where $n\geq 2$)and no vertices has degree of $2$, then $T$ has at least $\frac{n+2}{2}$ leaves. Prove by contradiction Suppose that $T$ has less than $\frac{n+...
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0answers
41 views

Diameter of subtrees

Can some one explain how this guy is calculating the centers of all subtrees in $O(n)$. I couldn't understand it. Here is the Quora link A part of his answer claims the following: 4) Find centre of ...
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1answer
54 views

Infinite graph theory: What's a tree?

Consider a finite graph $G$: $G$ is a tree if it satisfies any of the following equivalent conditions: (1) $G$ is connected and no cycle can be a subgraph of $G$. (2) $G$ is connected and no cycle ...
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0answers
14 views

number of nodes in Balance binary tree, Full binary tree Complete binary tree

How can I calculate the number the number of nodes in Balance binary tree, Full binary tree Complete binary tree? For the perfect binary Tree, I found the formula $2^{h+1}-1$.
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1answer
33 views

Verify directly that are exactly 125 labelled trees on 5 vertices.

I know Cayley's formula. However, I need to count them without using the formula. Such a tree has $5-1=4$ edges. Let the degrees of vertices be $d_1,d_2,d_3,d_4,d_5$. By handshaking lemma $d_1+d_2+d_3+...
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1answer
21 views

Maximum number of strict binary trees that can be made, each having exactly n leaf nodes.

I am trying to evaluate(Mathematical expression) the number of strict binary trees that can be made with n leaf nodes. I already know that a strict binary tree with n leaf nodes would have exactly ...
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0answers
20 views

Uniqueness of spanning trees made using search algorithms?

For undirected graphs, the corresponding spanning trees can be obtained using various search algorithms like Depth-first search algorithm , Bredth-first algorithm, etc. I am not sure whether the ...
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1answer
63 views

Is this a Red-Black Tree?

I tried to build RBT (Red-Black Tree) via this way: I build a balanced binary search tree (much as I can) and then colored it... Now the Q is: if this is a legal RBT? At my opinion is yes, because ...
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1answer
33 views

How to define a set of trees recursively?

In particular, consider the set of integer-labelled binary trees (T). How could this set be defined in a recursive way from $\mathbb Z$ and T itself? Examples: $(-2, 1, (3, 1, 0)) \in T$ $(-1, (7, 2, ...
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1answer
61 views

How do I know when to use a Venn diagram or a probability tree? Also, when can I assume that the events are independent?

I have 2 specific problems, one 'requiring' me to use a probability tree, and the other a Venn diagram. I know that apparently the Venn diagrams can be converted into probability trees and vice versa, ...
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1answer
193 views

Find tree diameter or center

I want to find center in a graph that doesn't have cycles. I heard, that this is how I find a diameter: Take random vertex A Find such vertex B, that distance to it is maximal Find such vertex C, ...
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1answer
34 views

What function describes this problem of every possible breeding of a set of dogs?

If I have n dogs [a, b, c, ...], and I want to breed them in every possible combination (every possible binary tree made of ...
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1answer
25 views

Bounding the probability of landing at any point for a random walk on a tree

Fix $m\geq 2$ and a vertex $v_0$ in an infinite connected $2m$-regular tree, (in other words, the Cayley graph for the free group on $m$ generators) and consider the random walk on the tree starting ...
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0answers
24 views

Are these tree-related concepts redundant?

I've been doing a lot of work with trees lately, and have developed vocabulary that I've been using to describe them. Not having that strong of a background in graph theory, it occurred to me that I ...