Solution.cpp

class Trie {
public:
    vector<Trie*> children;
    bool isEnd;

    Trie() {
        children.resize(128);
        isEnd = false;
    }

    void insert(string word) {
        Trie* node = this;
        for (char c : word) {
            if (!node->children[c]) node->children[c] = new Trie();
            node = node->children[c];
        }
        node->isEnd = true;
    }
};

class Solution {
public:
    string boldWords(vector<string>& words, string s) {
        Trie* trie = new Trie();
        for (string w : words) trie->insert(w);
        int n = s.size();
        vector<pair<int, int>> pairs;
        for (int i = 0; i < n; ++i) {
            Trie* node = trie;
            for (int j = i; j < n; ++j) {
                int idx = s[j];
                if (!node->children[idx]) break;
                node = node->children[idx];
                if (node->isEnd) pairs.push_back({i, j});
            }
        }
        if (pairs.empty()) return s;
        vector<pair<int, int>> t;
        int st = pairs[0].first, ed = pairs[0].second;
        for (int i = 1; i < pairs.size(); ++i) {
            int a = pairs[i].first, b = pairs[i].second;
            if (ed + 1 < a) {
                t.push_back({st, ed});
                st = a, ed = b;
            } else
                ed = max(ed, b);
        }
        t.push_back({st, ed});
        string ans = "";
        int i = 0, j = 0;
        while (i < n) {
            if (j == t.size()) {
                ans += s.substr(i);
                break;
            }
            st = t[j].first, ed = t[j].second;
            if (i < st) ans += s.substr(i, st - i);
            ans += "<b>";
            ans += s.substr(st, ed - st + 1);
            ans += "</b>";
            i = ed + 1;
            ++j;
        }
        return ans;
    }
};