bool existHelper(vector<vector<bool> > &used, int x, int y, vector<vector<char> > &board, int start, string word) {
if (start == word.size()) return true;
if (x < 0 || x >= board.size() ||
y < 0 || y >= board[x].size() ||
board[x][y] != word[start] ||
used[x][y]) return false;
used[x][y] = true;
if (existHelper(used, x + 1, y, board, start + 1, word) ||
existHelper(used, x, y + 1, board, start + 1, word) ||
existHelper(used, x - 1, y, board, start + 1, word) ||
existHelper(used, x, y - 1, board, start + 1, word)) return true;
used[x][y] = false;
return false;
}
bool exist(vector<vector<char> > &board, string word) {
if (board.size() == 0) return false;
vector<vector<bool> > used;
for (int i = 0; i < board.size(); ++i) {
used.push_back(vector<bool>(board[i].size(), false));
for (int j = 0; j < board[0].size(); ++j) {
if (board[i][j] == word[0]) {
if (existHelper(used, i, j, board, 0, word)) return true;
}
}
}
return false;
}
bool existHelper(vector<vector<bool>> &visited,vector<vector<char>> &board,
string word,int index,int r,int c){
if (index == word.size()) return true;
vector<pair<int, int>> candis = generateCandidates(visited, board, word, index, r, c);
for (pair<int, int> cand : candis) {
int tmp_r = cand.first;
int tmp_c = cand.second;
visited[tmp_r][tmp_c] = true;
if (existHelper(visited, board, word, index+1, tmp_r, tmp_c)) return true;
visited[tmp_r][tmp_c] = false;
}
return false;
}
bool exist(vector<vector<char> > &board, string word) {
if (word.empty()) return false;
row = (int)board.size();
col = (int)board[0].size();
vector<vector<bool>> visited = createVisited(col, row);
for (int i = 0; i < row; i++) {
for (int j = 0; j < col; j++) {
if (board[i][j] == word[0]) {
visited[i][j] = true;
if (existHelper(visited,board,word,1,i,j)) return true;
visited[i][j] = false;
}
}
}
return false;
}
