Update add-bold-tag-in-string.cpp

Author: kamyu104

C++/add-bold-tag-in-string.cpp

@@ -1,6 +1,7 @@
-// Time:  O(s * d * l), l is the average string length
-// Space: O(s)
+// Time:  O(n * d * l), l is the average string length
+// Space: O(n)
 
+// 16ms
 class Solution {
 public:
     string addBoldTag(string s, vector<string>& dict) {
@@ -24,3 +25,71 @@ class Solution {
         return result;
     }
 };
+
+// Time:  O(n * l), l is the average string length
+// Space: O(t)    , t is the size of trie
+// 142ms
+class Solution2 {
+public:
+    string addBoldTag(string s, vector<string>& dict) {
+        TrieNode trie;
+        for (const auto& word : dict) {
+            trie.Insert(word);
+        }
+
+        vector<bool> lookup(s.length());
+        for (int i = 0; i < s.length(); ++i) {
+            auto curr = &trie;
+            int k = i - 1;
+            for (int j = i; j < s.length(); ++j) {
+                if (!curr->leaves.count(s[j])) {
+                    break;
+                }
+                curr = curr->leaves[s[j]];
+                if (curr->isString) {
+                    k = j;
+                }
+            }
+            fill(lookup.begin() + i, lookup.begin() + k + 1, true);
+        }
+
+        string result;
+        for (int i = 0; i < s.length(); ++i) {
+            if (lookup[i] && (i == 0 || !lookup[i - 1])) {
+                result += "<b>";
+            }
+            result.push_back(s[i]);
+            if (lookup[i] && (i == (s.length() - 1) || !lookup[i + 1])) {
+                result += "</b>";
+            }
+        }
+        return result;
+    }
+
+private:
+    struct TrieNode {
+        bool isString;
+        unordered_map<char, TrieNode *> leaves;
+        
+        TrieNode() : isString{false} {}
+        
+        void Insert(const string& s) {
+            auto* p = this;
+            for (const auto& c : s) {
+                if (!p->leaves[c]) {
+                    p->leaves[c] = new TrieNode;
+                }
+                p = p->leaves[c];
+            }
+            p->isString = true;
+        }
+        
+        ~TrieNode() {
+            for (auto& kvp : leaves) {
+                if (kvp.second) {
+                    delete kvp.second;
+                }
+            }
+        }
+    };
+};