22

15

3214

21

1016Liskeard

Launceston

Callington

St Austell

Bodmin

StarterFind the quickest route from St Austell to Launceston

Dijkstra’s Algorithm

Aims:To be able to use Dijkstra’s algorithm to find the shortest path between two vertices on a

network

Dijkstra’s Algorithm

• Invented by Edgar Dijkstra.• Dutch computer scientist.• Lived from 1930 to 2002.• Worked at the University

of Texas at Austin.• Received many awards for

his work in computer science.

Dijkstra’s Algorithm

• Is used to find the shortest path between two places.

• It does this by using temporary labels.• These keep track on the best way to get to

each place.• When you are sure you have the shortest way

you can make this a permanent label.• Let’s have a go!

22

15

3214

21

1016Liskeard

Launceton

Callington

St Austell

Bodmin

Use Dijkstra’s Algorithmto find the quickest route from St Austell to Launceston

Dijkstra’s Step-by-Step1) Label the starting vertex with 0. Place in a square box to

show a permanent label.2) Consider every vertex that connects to the starting and give

a temporary label.3) Put a box around the shortest temporary label, making it a

permanent label.4) Consider every place that connects to the new permanent

label. a) Add temporary labels to places that do not have one. b) If there is a shorter way to get to a place already temporary

labelled cross out and write the sorter distance down. c) If the distance is longer than the existing label do nothing .

5) Repeat steps 3 and 4 until complete.6) Follow the backwards to find the shortest route.

A B

C

D

E

F

2

2

21

1

55

5

64

4

Find the shortest path from A to F and state the route taken.

Find the shortest path from A to G and state the route taken.

Find the shortest path from A to G and state the route taken.

Find the shortest path from F to C and state the route taken.