IT235 Discrete Structure

Discrete StructureTU Board 2023

Using Dijkstra's Algorithm, find the shortest distance from source vertex 'A' to 'D' and 'E' in the following graph. [figure in the original paper]

3

Answer

42158102ABCDE
Given weighted graph (undirected, weights shown on edges)

Step-by-Step Application of Dijkstra’s Algorithm (Source = A)

Initialization

  • Set distance to source as 0, all others as .
  • Set all vertices as unvisited.
  • Initialize priority queue with .
Vertex Distance Visited
A 0 No
B ∞ No
C ∞ No
D ∞ No
E ∞ No

Iteration 1: Extract A (distance = 0)

  • Update neighbors of :
    • :
    • :
  • Mark as visited.
Vertex Distance Visited
B 4 No
C 2 No
D ∞ No
E ∞ No

Iteration 2: Extract C (smallest distance = 2)

  • Update neighbors of :
    • : (no change, since 3 > 4)
    • :
    • :
  • Mark as visited.
Vertex Distance Visited
B 3 No
D 10 No
E 12 No

Iteration 3: Extract B (distance = 3)

  • Update neighbors of :
    • :
  • Mark as visited.
Vertex Distance Visited
D 8 No
E 12 No

Iteration 4: Extract D (distance = 8)

  • Update neighbor of :
    • :
  • Mark as visited.
Vertex Distance Visited
E 10 No

Iteration 5: Extract E (distance = 10)

  • No updates needed.
  • Mark as visited.

Final Shortest Distances

  • Distance from A to D: 8 (Path: )
  • Distance from A to E: 10 (Path: )
42158102ABCDE
Shortest paths highlighted (A→D: 8, A→E: 10)

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