---
title: "#79 Word Search"
tags: LeetCode, Top100
---
#79 Word Search
==

題目描述
--
Given a 2D board and a word, find if the 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

解題思維
--
DFS

DFS
--

class Solution:
    def exist(self, board: List[List[str]], word: str) -> bool:
        def dfs(point, i, j):
            if point == k:
                return True
            if i < 0 or i >= m or j < 0 or j >= n:
                return False
            tmp = board[i][j]
            if tmp != word[point]:
                return False

            board[i][j] = '#'
            for x, y in [[0, -1],  [0, 1], [-1, 0], [1, 0]]:
                if dfs(point+1, i+x, j+y):
                    return True
            board[i][j] = tmp

        m = len(board)
        n = len(board[0])
        k = len(word)
        for i in range(m):
            for j in range(n):
                if dfs(0, i, j):
                    return True
        return False