LeetCode 79 Word Search

class Solution {
public:
    int vis[1005][1005];
    int dir[4][2]={{0,1},{0,-1},{1,0},{-1,0}};
    bool exist(vector<vector<char>>& board, string word) {
        
        if(word.length()==0)
            return false;
        for(int i=0;i<board.size();i++)
        {
            for(int j=0;j<board[i].size();j++)
            {
               if(board[i][j]==word[0])
               {
                   vis[i][j]=1;
                   bool ans=dfs(word,board,i,j,1);
                   
                   if(ans==true)
                       return true;
                   vis[i][j]=0;
               }
            }
        }
        
        return false;
    }
    
    bool dfs(string word,vector<vector<char>> board,int x,int y,int k)
    {
        if(k==word.length())
        {
            return true;
        }
        for(int i=0;i<4;i++)
        {
            x+=dir[i][0];
            y+=dir[i][1];
            
            if(x>=0&&x<board.size()&&y>=0&&y<board[0].size()
              &&vis[x][y]==0)
            {
                if(board[x][y]==word[k])
                {
                    vis[x][y]=1;
                    bool res= dfs(word,board,x,y,k+1);
                    vis[x][y]=0;
                 
                    
                    if(res==true)
                        return true;
                }
            }
            
            x-=dir[i][0];
            y-=dir[i][1];
        }
        return false;
    }
};