Word Search II
Hard
Array
String
Backtracking
Trie
Matrix
Given an `m x n` `board` of characters and a list of strings `words`, return *all words on the board*. Each word must be constructed from letters of sequentially adjacent cells, where adjacent cells are horizontally or vertically neighboring. The same letter cell may not be used more than once in a word.
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"]
Example 2
Input: board = [["a","b"],["c","d"]], words = ["abcb"]
Output: []

Constraints

  • •m == board.length
  • •n == board[i].length
  • •1 <= m, n <= 12
  • •board[i][j] is a lowercase English letter.
  • •1 <= words.length <= 3 * 10⁴
  • •1 <= words[i].length <= 10
  • •words[i] consists of lowercase English letters.
  • •All words[i] are unique.
Time Complexity
O(m*n*4^L)
Space Complexity
O(W*L)
14
Case 1
Input: [["o","a","a","n"],["e","t","a","e"],["i","h","k","r"],["i","f","l","v"]] ["oath","pea","eat","rain"]
Expected: [eat,oath]
Case 2
Input: [["a","b"],["c","d"]] ["abcb"]
Expected: []
Case 3
Input: [["a","a"]] ["a"]
Expected: [a]