Session 4 (2018_12_25 05_40_40 UTC).pptx

# Session 4 (2018_12_25 05_40_40 UTC).pptx - Session 4...

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Session 4 Uninformed Search 1

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Breadth First Search Algorithm: 1. Create a variable called NODE-LIST and set it to initial state 2. Until a goal state is found or NODE-LIST is empty do a. Remove the first element from NODE-LIST and call it E. If NODE-LIST was empty, quit b. For each way that each rule can match the state described in E do: i. Apply the rule to generate a new state ii. If the new state is a goal state, quit and return this state iii. Otherwise, add the new state to the end of NODE-LIST 2
BFS Tree for Water Jug problem (0,0) (4,0) (0,3) (4,3) (0,0) (1,3) (4,3) (0,0) (3,0) 3

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Advantages of BFS BFS will not get trapped exploring a blind alley. If there is a solution, BFS is guarnateed to find it. If there are multiple solutions, then a minimal solution will be found. 4
Uniform Cost Search 5

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6 Uniform Cost Search is the best algorithm for a search problem, which does not involve the use of heuristics. It can solve any general graph for optimal cost. Uniform Cost Search as it sounds searches in branches which are more or less the same in cost. Uniform Cost Search again demands the use of a priority queue. Recall that Depth First Search used a priority queue with the depth upto a particular node being the priority and the path from the root to the node being the element stored. The priority queue used here is similar with the priority being the cumulative cost upto the node. Unlike Depth First Search where the maximum depth had the maximum priority, Uniform Cost Search gives the minimum cumulative cost the maximum priority.
7 The algorithm using this priority queue is the following: Insert the root into the queue While the queue is not empty Dequeue the maximum priority element from the queue (If priorities are same, alphabetically smaller path is chosen) If the path is ending in the goal state, print the path and exit Else Insert all the children of the dequeued element, with the cumulative costs as priority

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• Spring '19
• Dr. Anjali Mathur
• Depth-first search, Search algorithm

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