Define Informed Search. Explain Greedy Best-First Search and A algorithm with heuristics.*

Answer:

Informed search (heuristic search) uses additional knowledge (heuristics) to guide search more efficiently.

A heuristic function h(n) estimates the cost from node n to the goal.

Greedy Best-First Search:

  • Selects node with the lowest h(n).
  • Fast but not always optimal.
  • Can get stuck in local minima.

A* Search:

  • Uses evaluation function: f(n) = g(n) + h(n)
    • g(n) is cost so far,
    • h(n) is estimated cost to goal.
  • Optimal and complete if h(n) is admissible (never overestimates).

Example Heuristics:

  • For 8-puzzle:
    • h₁: number of misplaced tiles.
    • h₂: Manhattan distance (sum of row and column differences).

A* search is efficient and widely used in AI applications

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