剑指 Offer 12. 矩阵中的路径

剑指 Offer 12. 矩阵中的路径

class Solution {
public:
    unsigned int len1, len2;
    bool exist(vector<vector<char>>& board, string word) {
        len1 = board.size();
        if(len1 == 0) return false;
        len2 = board[0].size();
        if(len2 == 0) return false;
        vector<vector<int>> visited(len1, vector<int>(len2, 0));
        for(int i = 0; i < len1; i++) {
            for(int j = 0; j < len2; j++) {
                if(helper(board, i, j, word, 0, visited)) {
                    return true;
                }
            }
        }
        return false;
    }
private:
    bool helper(vector<vector<char>>& board, int row, int col, string word, int k, vector<vector<int>>& visited) {
        if(k == word.length() - 1) {
            return board[row][col] == word[k];
        }
        //方向数组
        int direction[4][2] = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
        if(board[row][col] == word[k]) {
            visited[row][col] = 1;
            for(int i = 0; i < 4; i++) {
                int dx = row + direction[i][0];
                int dy = col + direction[i][1];
                if(dx >= 0 && dx < len1 && dy >= 0 && dy < len2 && !visited[dx][dy]) {
                    if(helper(board, dx, dy, word, k + 1, visited)) {
                        return true;
                    }
                }
            }
            visited[row][col] = 0;
        }
        return false;
    }
};