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Trie / Backtracking•Pattern: Backtracking•Medium

Word Search in a 2D grid

Problem Intuition & Objective

Determine if a word can be constructed from adjacent cells in a grid.

Time ComplexityO(m×n×4^L) worst case
Optimal
Space ComplexityO(L) recursion stack
Memory Bounds
Optimal Algorithmic Approach

DFS + backtracking with visited marking.

Core Invariants & Edge Cases

  • DFS/backtracking from every cell that matches word[0]
  • Mark visited cells temporarily to avoid revisiting
  • For multiple words: build a Trie and search simultaneously
Previous ProblemImplement a Trie (Prefix Tree)Next Problem Kth largest element in a stream

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