Add solution: 720. Longest Word in Dictionary

leetcodes/720-longest-word-in-dictionary/720.cpp

@@ -0,0 +1,41 @@
+struct TrieNode {
+  vector<shared_ptr<TrieNode>> children;
+  const string* word = nullptr;
+  TrieNode() : children(26) {}
+};
+
+class Solution {
+ public:
+  string longestWord(vector<string>& words) {
+    for (const string& word : words)
+      insert(word);
+    return longestWordFrom(root);
+  }
+
+ private:
+  shared_ptr<TrieNode> root = make_shared<TrieNode>();
+
+  void insert(const string& word) {
+    shared_ptr<TrieNode> node = root;
+    for (const char c : word) {
+      const int i = c - 'a';
+      if (node->children[i] == nullptr)
+        node->children[i] = make_shared<TrieNode>();
+      node = node->children[i];
+    }
+    node->word = &word;
+  }
+
+  string longestWordFrom(shared_ptr<TrieNode> node) {
+    string ans = node->word ? *node->word : "";
+
+    for (shared_ptr<TrieNode> child : node->children)
+      if (child && child->word) {
+        string childWord = longestWordFrom(child);
+        if (childWord.length() > ans.length())
+          ans = childWord;
+      }
+
+    return ans;
+  }
+};

leetcodes/720-longest-word-in-dictionary/720.java

@@ -0,0 +1,38 @@
+class TrieNode {
+  public TrieNode[] children = new TrieNode[26];
+  public String word;
+}
+
+class Solution {
+  public String longestWord(String[] words) {
+    for (final String word : words)
+      insert(word);
+    return longestWordFrom(root);
+  }
+
+  private TrieNode root = new TrieNode();
+
+  private void insert(final String word) {
+    TrieNode node = root;
+    for (char c : word.toCharArray()) {
+      final int i = c - 'a';
+      if (node.children[i] == null)
+        node.children[i] = new TrieNode();
+      node = node.children[i];
+    }
+    node.word = word;
+  }
+
+  private String longestWordFrom(TrieNode node) {
+    String ans = node.word == null ? "" : node.word;
+
+    for (TrieNode child : node.children)
+      if (child != null && child.word != null) {
+        String childWord = longestWordFrom(child);
+        if (childWord.length() > ans.length())
+          ans = childWord;
+      }
+
+    return ans;
+  }
+}

leetcodes/720-longest-word-in-dictionary/720.py

@@ -0,0 +1,25 @@
+class Solution:
+  def longestWord(self, words: list[str]) -> str:
+    root = {}
+
+    for word in words:
+      node = root
+      for c in word:
+        if c not in node:
+          node[c] = {}
+        node = node[c]
+      node['word'] = word
+
+    def dfs(node: dict) -> str:
+      ans = node['word'] if 'word' in node else ''
+
+      for child in node:
+        if 'word' in node[child] and len(node[child]['word']) > 0:
+          childWord = dfs(node[child])
+          if len(childWord) > len(ans) or (
+                  len(childWord) == len(ans) and childWord < ans):
+            ans = childWord
+
+      return ans
+
+    return dfs(root)