leetcode [79] Word Search

class Solution {
public:
    vector<vector<int>>dir={{-1,0},{1,0},{0,-1},{0,1}};
    bool search(vector<vector<char>>& board,int i,int j,vector<vector<bool>>&visited,string word,int index){
        if(index==word.size()) return true;
        if(i<0||i>=board.size()||j<0||j>=board[0].size()||visited[i][j]) return false;
        if(board[i][j]!=word[index]) return false;
        visited[i][j]=true;
        for(int m=0;m<4;m++){
            int x=i+dir[m][0];
            int y=j+dir[m][1];
            if(search(board,x,y,visited,word,index+1)) return true;
        }
        visited[i][j]=false;
        return false;
    }
    bool exist(vector<vector<char>>& board, string word) {
        int m=board.size(),n=board[0].size();
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                vector<vector<bool>>visited(m,vector<bool>(n,false));
                if(board[i][j]==word[0] && search(board,i,j,visited,word,0)) return true;
            }
        }
        return false;
    }
};

class Solution {
public:
    bool search(vector<vector<char>>&board,int i,int j,string word,int index){
        if(index==word.size()) return true;
        if(i<0||i>=board.size()||j<0||j>=board[0].size()) return false;
        char c=board[i][j];
        if(c==word[index]){
            board[i][j]=‘#‘;
            if(search(board,i+1,j,word,index+1)) return true;
            if(search(board,i,j+1,word,index+1)) return true;
            if(search(board,i-1,j,word,index+1)) return true;
            if(search(board,i,j-1,word,index+1)) return true;
            board[i][j]=c;
        }
        return false;
    }

    bool exist(vector<vector<char>>& board, string word) {
        int m=board.size(),n=board[0].size();
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                if(search(board,i,j,word,0)) return true;
            }
        }
        return false;
    }
};

class Solution(object):
    def search(self,board,i,j,word):
        if len(word)==0:
            return True
        if i<0 or i>=len(board) or j<0 or j>=len(board[0]) or board[i][j]!=word[0]:
            return False
        tmp=board[i][j]
        board[i][j]="#"
        res=(self.search(board,i+1,j,word[1:]) or self.search(board,i,j+1,word[1:]) or self.search(board,i-1,j,word[1:]) or self.search(board,i,j-1,word[1:]))
        board[i][j]=tmp

        return res

    def exist(self, board, word):
        """
        :type board: List[List[str]]
        :type word: str
        :rtype: bool
        """
        if board is None:
            return False
        m,n=len(board),len(board[0])
        for i in xrange(m):
            for j in xrange(n):
                if self.search(board,i,j,word):
                    return True
        return False