Word Search

//https://leetcode.com/problems/word-search/
class Solution {
public:
    bool exist(vector<vector<char>>& board, string word) {

        for(int i = 0; i < board.size(); ++i) {
            for(int j = 0; j < board[i].size(); ++j) {
                if(board[i][j] == word[0]) {
                    std::vector<std::vector<bool>> visited_array(board.size(), std::vector<bool>(board[0].size(), false));
                    bool word_exists =  exists(board, visited_array, i,j, word, 0);
                    if(word_exists)
                        return true;

                }
            }
        }
        return false;
    }
private:
    bool exists(std::vector<std::vector<char>> &board, std::vector<std::vector<bool>> & visited_array, int r, int c, std::string & word, int current_index) {
        if(current_index == word.size())
            return true;

        if(r < 0 || r >= board.size())
            return false;
        if(c <0 || c >= board[0].size())
            return false;

        if(board[r][c] == word[current_index] && visited_array[r][c] == false) {
            visited_array[r][c] = true;
            bool is_whole_word_present = exists(board, visited_array, r+1,c, word, current_index+1) ||
                exists(board, visited_array, r,c+1, word, current_index+1) ||
                exists(board, visited_array, r-1,c, word, current_index+1) ||
                exists(board, visited_array, r,c-1, word, current_index+1);
            if(is_whole_word_present)
                return true;
            visited_array[r][c] = false;
        }

        return false;

    }

};