Word Search
Medium
Array
Backtracking
Matrix
Given an `m x n` grid of characters `board` and a string `word`, return `true` *if* `word` *exists in the grid*. The word can 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.
Example 1
Input: board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "ABCCED"
Output: true
Example 2
Input: board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "SEE"
Output: true
Example 3
Input: board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "ABCB"
Output: false

Constraints

  • •m == board.length
  • •n == board[i].length
  • •1 <= m, n <= 6
  • •1 <= word.length <= 15
  • •board and word consist of only lowercase and uppercase English letters.
Time Complexity
O(m*n*4^L)
Space Complexity
O(L)
14
Case 1
Input: [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]] ABCCED
Expected: true
Case 2
Input: [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]] SEE
Expected: true
Case 3
Input: [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]] ABCB
Expected: false