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Word Search II
Certification: Advanced Level
Accuracy: 0%
Submissions: 0
Points: 20
Write a C++ program to implement Word Search II to find all words from a dictionary that can be formed by sequentially adjacent letters on a grid.
Example 1
- Input:
board = [['o','a','a','n'], ['e','t','a','e'], ['i','h','k','r'], ['i','f','l','v']]
words = ["oath","pea","eat","rain"] - Output: ["eat","oath"]
- Explanation:
- "eat" and "oath" can be formed using adjacent cells.
Example 2
- Input:
board = [['a','b'], ['c','d']]
words = ["abcb","ab","cd","ac","bd"] - Output: ["ab","ac","bd","cd"]
- Explanation:
- "abcb" cannot be formed without reusing letters.
Constraints
- 1 ≤ m, n ≤ 12
- 1 ≤ words.length ≤ 3×10⁴
- Each word has max length 10
- All board letters and words are lowercase
- Time Complexity: O(m*n*4^L) where L is the maximum word length
- Space Complexity: O(total characters in words)
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Solution Hints
- Use a Trie data structure to store all the words for efficient prefix matching
- Implement a depth-first search (DFS) to explore all possible paths on the board
- Track visited cells during the search to avoid using the same cell twice
- Optimize by pruning search paths that cannot form any word in the dictionary
- Use a set to store found words to avoid duplicates