[Python3] Backtracking
\nclass Solution:\n    def exist(self, board: List[List[str]], word: str) -> bool:\n        for i in range(len(board)):\n            for j in range(len(board[i]
```\nclass Solution:\n    def exist(self, board: List[List[str]], word: str) -> bool:\n        for i in range(len(board)):\n            for j in range(len(board[i])):\n                if self.backtracking(i, j,word,board):\n                    return True\n        return False\n    def backtracking(self,i, j,word,board):\n            if len(word) == 0:\n                return True\n            if i < 0 or i >= len(board) or j < 0 or j >= len(board[i]):\n                return False\n            if board[i][j] == word[0]:\n                board[i][j] = "~"\n                if self.backtracking(i+1, j, word[1:],board) or self.backtracking(i-1, j, word[1:],board) or self.backtracking(i, j+1, word[1:],board) or self.backtracking( i, j-1, word[1:],board):\n                    return True\n                board[i][j] = word[0]\n            return False\n```
['Backtracking', 'Python', 'Python3']