Lecture 3: UniformCost Search and A*Mark Hasegawa-Johnson, January 2021With some slides by Svetlana Lazebnik, 9/2016Distributed under CC-BY 3.0Title image: By Harrison Weir - From reuseableart.com,Public Domain,https://commons.wikimedia.org/w/index.php?curid=47879234Review: DFS and BFS• Breadth-first search• Frontier is a queue: expand the shallowest node• Complete: always finds a solution, if one exists• Optimal (finds the best solution) if all actions have the same cost.• Time complexity: 𝑂{𝑏 ! }• Space complexity: 𝑂{𝑏 ! }.• Depth-first search – utility depends on relationship between m and d• Frontier is a stack: expand the deepest node• Not complete (might never find a solution, if m is infinite)• Not optimal (returned solution is rarely the best one)• Time complexity: 𝑂{𝑏 " }• Space complexity: 𝑂{𝑏𝑚}.Outline of today’s lecture1. Uniform Cost Search (UCS): like BFS, but for actions that have differentcosts• Complete: always finds a solution, if one exists• Optimal: finds t...

**Title**

# Lecture 3: uniform cost search and a*

**Description**

Review: dfs and bfs ... uniform cost search (ucs): like bfs, but for actions that have different ... an example for which bfs is not optimal: romania.
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