find word in grid of characters. return true if the word exists

main.cpp

class Solution {
private: 
    
    bool dfs(vector<vector<char>>&board, int count, int i, int j, string& word)
    {
        if(word.size() == count) //Signifies that we have reached the end of search
            return true;
        if(i<0 || j<0 || i>=board.size() || j>=board[0].size() || board[i][j]!=word[count])
        return false;
        //We check if element is within bounds and then check if the character at that is the same as the corresponding character in string word


        char temp = board[i][j];
        board[i][j] = ' '; //To show that we have visited this node

        bool res = dfs(board, count+1, i+1, j, word) || dfs(board, count+1, i-1, j, word) || dfs(board, count+1, i, j+1, word) ||dfs(board, count+1, i, j-1, word); //DFS in all 4 directions

        board[i][j] = temp; //Restore the element after checking

        return res;
    }
    
public:
    bool exist(vector<vector<char>>& board, string word) {
        if(board.empty())   return false;
    
        for(int i = 0; i < board.size(); i++){
            for(int j = 0; j < board[i].size(); j++){
                if(dfs(board, 0, i, j,  word)) 
                    return true; 
            }
        }
        return false;
    }
        
};