Leetcode#79 Word Search

原题地址

依次枚举起始点，DFS+回溯

代码：

bool dfs(vector<vector<char> > &board, int r, int c, string word) {
  int m = board.size();
  int n = board[0].size();
  int dir[4][2] = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};

  if (word.empty())
    return true;

  if (r >= 0 && r < m && c >= 0 && c < n && board[r][c] == word[0]) {
    for (int i = 0; i < 4; i++) {
      char tmp = board[r][c];
      board[r][c] = 0;
      if (dfs(board, r + dir[i][0], c + dir[i][1], word.substr(1)))
        return true;
      board[r][c] = tmp;
    }
  }

  return false;
}

bool exist(vector<vector<char> > &board, string word) {
  if (board.empty() || board[0].empty()) return false;

  int m = board.size();
  int n = board[0].size();

  for (int i = 0; i < m; i++)
    for (int j = 0; j < n; j++)
      if (dfs(board, i, j, word))
        return true;

  return false;
}