LeetCode – Refresh – Word Search

From each pointer, spread to the board. One tricky is set the char that used to be 0. Set it back when finished searching.

class Solution {
private:
    bool found;
    int n, m;
public:
    void findWord(vector<vector<char> > &board, int index, int row, int column, string word) {
        if (word[index] != board[row][column] || found) {
            return;
        }
        if (index == word.size()-1) {
            found = true;
            return;
        }
        char tmp = board[row][column];
        board[row][column] = 0;
        if (row > 0) findWord(board, index+1, row-1, column, word);
        if (row < n-1) findWord(board, index+1, row+1, column, word);
        if (column > 0) findWord(board, index+1, row, column-1, word);
        if (column < m-1) findWord(board, index+1, row, column+1, word);
        board[row][column] = tmp;
    }
    bool exist(vector<vector<char> > &board, string word) {
        if (board.size() == 0) return false;
        n = board.size(), m = board[0].size();
        found = false;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                findWord(board, 0, i, j, word);
                if (found) return true;
            }
        }
        return false;
    }
};