The 7 Bridges of Königsberg Quiz
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Questions and Answers

What happens if adding an edge to a spanning tree generates a cycle?

  • The edge is temporarily included until all edges are considered.
  • The spanning tree is restructured to include the edge.
  • The edge is rejected and not included in the graph. (correct)
  • The edge is included in the graph.
  • In Kruskal's algorithm, what is the first step to be performed?

  • Identify all cycles in the current graph.
  • Start adding edges without sorting.
  • Sort the edges by increasing weight. (correct)
  • Select the edge with the maximum weight.
  • Why is cycle detection important in Kruskal's algorithm?

  • To ensure that all edges can connect any two vertices.
  • To verify that the spanning tree remains connected.
  • To prevent the inclusion of edges that would form a cycle. (correct)
  • To keep the total weight of the tree as low as possible.
  • When adding edges in Kruskal's algorithm, which edge is preferred first?

    <p>The edge that has the least weightage.</p> Signup and view all the answers

    What is the significance of arranging edges in increasing order of weight?

    <p>To ensure that the least costly options are considered first.</p> Signup and view all the answers

    What does the spanning tree property ensure?

    <p>There are no cycles, and all vertices are connected.</p> Signup and view all the answers

    Which technique is primarily used in Kruskal's algorithm?

    <p>Greedy approach.</p> Signup and view all the answers

    If an edge (E, G) is added and it creates a cycle, what should be done?

    <p>Discard the edge to maintain the spanning tree property.</p> Signup and view all the answers

    What condition must be satisfied for a graph to have an Euler circuit?

    <p>The graph must be connected and all vertices have even degrees.</p> Signup and view all the answers

    In the context of Eulerian paths, how many vertices can have an odd degree for such a path to exist?

    <p>Exactly two odd degree vertices.</p> Signup and view all the answers

    What defines an odd vertex in graph theory?

    <p>A vertex connected by an odd number of edges.</p> Signup and view all the answers

    Which of the following statements is true regarding Eulerian paths?

    <p>An Eulerian path traverses every edge exactly once.</p> Signup and view all the answers

    What is a defining characteristic of an Euler circuit?

    <p>It ends at the same vertex where it starts.</p> Signup and view all the answers

    When investigating the 7 Bridges of Königsberg problem, which conclusion did Euler reach?

    <p>It is impossible to traverse all bridges exactly once.</p> Signup and view all the answers

    Which theorem states that a finite graph can have an Euler path if it is connected and exactly two vertices have odd degrees?

    <p>Euler's Path Theorem.</p> Signup and view all the answers

    What is the implication of having all even degree vertices in a graph?

    <p>The graph can have an Euler circuit.</p> Signup and view all the answers

    What property must a minimum spanning tree possess regarding the number of edges?

    <p>It must have one less edge than the number of vertices.</p> Signup and view all the answers

    Which of the following statements best describes the greedy algorithm approach in finding a minimum spanning tree?

    <p>It selects edges based on the smallest weight while avoiding cycles.</p> Signup and view all the answers

    When sorting edges by weight for the purpose of creating a minimum spanning tree, what is the primary goal?

    <p>To minimize the total weight of the spanning tree.</p> Signup and view all the answers

    Which algorithm is commonly used for cycle detection in undirected graphs?

    <p>Depth-First Search (DFS)</p> Signup and view all the answers

    In a graph, which of the following conditions would suggest the presence of a cycle?

    <p>All vertices have an even degree.</p> Signup and view all the answers

    If a graph is acyclic and connected, what can be inferred about its structure?

    <p>It is a spanning tree.</p> Signup and view all the answers

    What role does a queue play in the breadth-first search (BFS) algorithm?

    <p>To manage the visited vertices during traversal.</p> Signup and view all the answers

    What is the primary concern when detecting cycles using the union-find method?

    <p>Ensuring subsets of the graph remain disjoint.</p> Signup and view all the answers

    When creating a minimum spanning tree using Kruskal's algorithm, which step is taken after sorting all edges?

    <p>Select the first edge and add it to the tree.</p> Signup and view all the answers

    What must be true of the edges selected in the process of forming a minimum spanning tree?

    <p>They must not create any cycles.</p> Signup and view all the answers

    Study Notes

    The 7 Bridges of Königsberg

    • Journey can start and finish at any point in the town.
    • The goal is to cross all seven bridges once and only once.
    • Represents a problem of drawing a network without lifting the pencil or retracing a line.
    • Euler defined odd and even vertices based on the number of arcs connected:
      • Odd vertex: odd number of arcs.
      • Even vertex: even number of arcs.
    • A graph has an Eulerian walk if it has either 0 or 2 odd degree vertices.

    Euler Circuits and Paths

    • Euler Circuit: A circuit that visits every edge in a graph. Requires connected graph with all vertices of even degree.
    • Euler Path: A path that visits every edge; requires connected graph with exactly two odd degree vertices.

    Graph Terminology

    • Graph G: An ordered pair of a set of vertices and a set of edges (2-subsets of vertices).
    • Simple Graph: No loops or multiple edges; consists only of distinct edges.
    • Directed Graph: Each edge has a direction, represented as ordered pairs (e.g., E = {(1,2), (3,2), (1,3)}).

    Edge and Vertex Terminology

    • Endpoints: U and V are the endpoints of an edge.
    • Incident Edges: Edges connected to a specific vertex.
    • Degree of a Vertex: The count of edges emerging from it (e.g., a vertex X has degree 5).
    • Parallel Edges: Edges connecting the same pair of vertices.
    • Self-loop: An edge that connects a vertex to itself.
    • Adjacent Vertices/Edges: Vertices or edges sharing a common endpoint.

    Path Definitions

    • Path: Sequence of alternating vertices and edges starting and ending with vertices.
    • Simple Path: A path where all vertices and edges are distinct.

    Graph Properties

    • Property 1: Each edge is counted twice in terms of its incidence on vertices.
    • Property 2: Degree of any vertex is limited in undirected graphs without self-loops or multiple edges.

    Graph Representation

    • Adjacency Matrix: Represents edges in a grid format with rows for vertices and columns for edges, using binary values (0 or 1).
    • Incidence Matrix: Shows the connection between vertices and edges where rows represent vertices and columns represent edges.

    Graph Traversal - Breadth-First Search (BFS)

    • Gather vertices level by level using a queue to manage which vertex to explore next.
    • If a dead-end is reached, backtrack to explore other vertices.
    • Spanning tree properties must hold; if not, the edge is excluded.

    Kruskal’s Algorithm

    • Step 1: Arrange all edges in increasing weight order.
    • Step 2: Select edges that do not cause a cycle when added to the graph.
    • Step 3: Start adding edges with the least weight to form a spanning tree, while ensuring no cycles are created.

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    Chapter 4 - Graph.pptx

    Description

    Test your understanding of the famous problem of the 7 Bridges of Königsberg. In this quiz, you will explore routes within the town, attempting to cross all seven bridges exactly once. Can you find a valid path without retracing your steps?

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