This document discusses three uninformed search algorithms: breadth-first search, depth-first search, and bidirectional search. It provides details on each: Breadth-first search expands the root node first, then all successors, using a FIFO queue. It is complete but not optimal. Depth-first search uses a stack and expands the deepest node first, making it incomplete but able to find solutions when breadth-first cannot due to space limits. Bidirectional search runs two simultaneous searches forward and backward from the initial and goal states, hoping they meet in the middle, making it complete and optimal.

1. uninformed search
10
Depth-First Search
Breadth-First Search
Bidirectional Search

2. Uninformed
Search
 Uninformed search algorithms do not
have additional information about state
or search space other than how to
traverse the tree, so it is also called
blind search.
 All they can do is generate successors and
distinguish a goal state from a non-goal
state
 Example: Breadth-first search.
Depth-first search
Bidirectional Search

3. Breadth-first search
 Breadth-first search is a simple strategy in
which the root node is expanded first, then all
the successors of the root node are expanded
next, then their successors, and so on.
 This is achieved very simply by using a FIFO
queue data structure.
 Level Search Technique.
 Complete.

4. A
F
B C
E G
D
OMega TechEd
A
BC
CDE
DEFG
EFG
H
A B C D
FGH
GH
H
E F G H
Tail
Breadth-First Search
Head

5. Depth-first search
 Depth first search (DFS) algorithm starts with
the initial node of the graph G, and then goes
to deeper and deeper until we find the goal
node or the node which has no children.
 Depth-first search always expands the deepest
node in the current frontier of the search tree.
 Depth-first search uses a LIFO .
 Use data structure stack.
 Incomplete
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6. A
F
B C
E G
D
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Depth-First Search
A
C
B
C
B
F
G
G
B
F
F
D
E
B E D
D
B
A

7. Bidirectional
search
 The idea behind bidirectional
search is to run two
simultaneous searches, one
forward from the initial state and
the other backward from the
goal, hoping that the two
searches meet in the middle.
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8. A
B
C
D
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Bidirectional Search
Initial
State
Goal State
F
E
H
G
I
Intersection
node

9. Comparison Of Uninformed Search Strategies
Criteriaon Breadth
First
Depth
First
Bidirectional
Complexity bd bm bd/2
Optimality Yes No Yes
Completeness Yes No Yes
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10. Thanks For
Watching
Reference:
Artificial Intelligence
A Modern Approach Third Edition
Peter Norvig and Stuart J. Russell
Next Topic:
Informed Search.
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