剑指offer12 矩阵中的路径

public boolean exist(char[][] board, String word){
        char[] array=word.toCharArray();
        for(int i=0;i<board.length;i++){
            for(int j=0;j<board[0].length;j++){
                if(dfs(i,j,0,array,board)) return true;
            }
        }
        return false;
    }

    public boolean dfs(int i,int j,int k,char[] word,char[][] board){
        if(i<0||i>=board.length||j<0||j>=board[0].length||word[k]!=board[i][j]) return false;
        if(k==word.length-1) return true;
        board[i][j]='\0';
        boolean res=dfs(i+1,j,k+1,word,board)||dfs(i,j+1,k+1,word,board)||dfs(i-1,j,k+1,word,board)||dfs(i,j-1,k+1,word,board);
        board[i][j]=word[k];
        return res;
    }