CSC 172 DATA STRUCTURES

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CSC 172 DATA STRUCTURES
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Traversing graphs

• Depth-First Search
• like a post-order traversal of a tree
• Breath-First Search
• Less like tree traversal

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Traversing graphs

• Depth-First Search
• like a post-order traversal of a tree
• Breath-First Search
• Less like tree traversal
• Priority-First Search
• Good for Shortest Path
• Dijkstra's Algorithm

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Breadth-First Search

• Unweighted Shortest Path
• Starting vertex has level 0 (anchor vertex)
• Visit (mark) all vertices that are only one edge
  away
• mark each vertex with its level
• One edge away from level 0 is level 1
• One edge away from level 1 is level 2
• Etc. . . .

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Example
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Example
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Example
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Example
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Example
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Example
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Example
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Example
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Example
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Example
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Example
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Example
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Example
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Example
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Example
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BFS Tree
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Dijkstra's Algorithm

• //
• for each Vertex v
• v.dist infinity
• v.known false

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Dijkstra's Algorithm

• while (there is an unknown vertex)
• v delMin() // get the next one off the
  queue
• v.known true
• for each Vertex w adjacent to v
• if (!w.known)
• if (v.dist dist_v2w lt w.dist)
• w.dist vdist dist_v2w
• enqueue(w)