单词搜索

给定一个二维网格和一个单词，找出该单词是否存在于网格中。

单词必须按照字母顺序，通过相邻的单元格内的字母构成，其中“相邻”单元格是那些水平相邻或垂直相邻的单元格。同一个单元格内的字母不允许被重复使用。

示例:

board =
[
['A','B','C','E'],
['S','F','C','S'],
['A','D','E','E']
]

给定 word = "ABCCED", 返回 true.
给定 word = "SEE", 返回 true.
给定 word = "ABCB", 返回 false.

class Solution {
    public boolean exist(char[][] board, String word) {
        int cur=0;
        boolean[][] visits = new boolean[board.length][board[0].length];
       
        for (int i=0; i<board.length; ++i){
            for (int j=0; j<board[i].length; ++j){
                if (check(board, i, j, cur, word, visits)){
                    return true;
                }
            }
        }
        return false;
    }
    
    public boolean check(char[][] board, int row, int col, int cur, String word, boolean[][] visits){
        if (cur == word.length()){
            return true;
        }
        
        boolean hasPath = false;
        if (row >=0 && col >= 0 && row < board.length && col < board[0].length && word.charAt(cur) == board[row][col] && !visits[row][col]){
                visits[row][col] = true;
                //cur++;
                hasPath = (check(board, row+1, col, cur+1, word, visits) || check(board, row, col+1, cur+1, word, visits)|| check(board, row-1, col, cur+1, word, visits) || check(board, row, col-1, cur+1, word, visits));
            
             if(!hasPath){
               // cur--;
                visits[row][col] = false;
            }
        }
        return hasPath;
    }
}