【leetcode 前缀树（字典树） C++】212. Word Search II

212. Word Search II

class TrieNode {
    
    
public:
    bool is_end;
    vector<TrieNode*> children = vector<TrieNode*>(26, nullptr);
    TrieNode() {
    
     is_end = false; }
};


class Solution {
    
    
public:
    TrieNode* root = new TrieNode();

    void insert(string word) {
    
    
        TrieNode* p = root;
        for(int ii = 0; ii < word.size(); ii++) {
    
    
            if(!p->children[word[ii] - 'a']) p->children[word[ii] - 'a'] = new TrieNode();
            p = p->children[word[ii] - 'a'];
        }
        p->is_end = true;
    }

    set<string> S;
    int H, W;
    vector<vector<char> > g_board;
    bool visited[12][12] = {
    
    false};
    void dfs(string str, TrieNode* p, int y, int x) {
    
    
        if(y < 0 || x < 0 || y >= H || x >= W || visited[y][x] || !p->children[g_board[y][x] - 'a']) return ;
        p = p->children[g_board[y][x] - 'a'];
        str += g_board[y][x];
        if(p->is_end) S.insert(str);
        visited[y][x] = true;
        dfs(str, p, y-1, x);
        dfs(str, p, y+1, x);
        dfs(str, p, y, x-1);
        dfs(str, p, y, x+1);
        visited[y][x] = false;
    }
    vector<string> findWords(vector<vector<char>>& board, vector<string>& words) {
    
    
        for(auto &word : words) insert(word);
        H = board.size(), W = board[0].size();
        g_board = board;
        for(int ii = 0; ii < H; ii++) {
    
    
            for(int jj = 0; jj < W; jj++) {
    
    
                dfs("", root, ii, jj);
            }
        }
        vector<string> result(S.begin(), S.end());
        return result;
    }
};