79.Word-Search.md

79. Word Search

題目

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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 consists of only lowercase and uppercase English letters.

思路

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Code

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• GoLang

  Runtime 375ms **Beats 25.83%**of users with Go

  Memory 2.11MB **Beats 26.82%**of users with Go

  func exist(board [][]byte, word string) bool {
      rows, cols := len(board), len(board[0])
      visited := make(map[int]bool)
      var backtracking func(row, col int, target string) bool
      backtracking = func(row, col int, target string) bool {
          if row < 0 || row >= rows ||
             col < 0 || col >= cols ||
             visited[row*cols + col] ||
             target[0] != board[row][col]  {
                 return false
          }
  
          target = target[1:len(target)]
          visited[row*cols + col] = true
  
          if target == "" {
              return true
          }
  
          isExisted := backtracking(row + 1, col, target) ||
              backtracking(row - 1, col, target) ||
              backtracking(row, col + 1, target) ||
              backtracking(row, col - 1, target)
  
          visited[row*cols + col] = false
  
          return isExisted
      }
  
      for r := 0; r < rows; r++ {
          for c := 0; c < cols; c++ {
              if backtracking(r, c, word) {
                  return true
              }
          }
      }
  
      return false
  }

Reference

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• https://www.youtube.com/watch?v=pfiQ_PS1g8E&ab_channel=NeetCode