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3043. Find the Length of the Longest Common Prefix 👍

  • Time: $O(|\texttt{arr1}| + |\texttt{arr2}|)$
  • Space: $O(|\texttt{arr1}| + |\texttt{arr2}|)$
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struct TrieNode {
  vector<shared_ptr<TrieNode>> children;
  TrieNode() : children(10) {}
};

class Trie {
 public:
  void insert(const string& word) {
    shared_ptr<TrieNode> node = root;
    for (const char c : word) {
      const int i = c - '0';
      if (node->children[i] == nullptr)
        node->children[i] = make_shared<TrieNode>();
      node = node->children[i];
    }
  }

  int search(const string& word) {
    int prefixLength = 0;
    shared_ptr<TrieNode> node = root;
    for (const char c : word) {
      const int i = c - '0';
      if (node->children[i] == nullptr)
        break;
      node = node->children[i];
      ++prefixLength;
    }
    return prefixLength;
  }

 private:
  shared_ptr<TrieNode> root = make_shared<TrieNode>();
};

class Solution {
 public:
  int longestCommonPrefix(vector<int>& arr1, vector<int>& arr2) {
    int ans = 0;
    Trie trie;

    for (const int num : arr1)
      trie.insert(to_string(num));

    for (const int num : arr2)
      ans = max(ans, trie.search(to_string(num)));

    return ans;
  }
};

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class TrieNode {
  public TrieNode[] children = new TrieNode[10];
}

class Trie {
  public void insert(final String word) {
    TrieNode node = root;
    for (final char c : word.toCharArray()) {
      final int i = c - '0';
      if (node.children[i] == null)
        node.children[i] = new TrieNode();
      node = node.children[i];
    }
  }

  public int search(final String word) {
    int prefixLength = 0;
    TrieNode node = root;
    for (final char c : word.toCharArray()) {
      final int i = c - '0';
      if (node.children[i] == null)
        break;
      node = node.children[i];
      ++prefixLength;
    }
    return prefixLength;
  }

  private TrieNode root = new TrieNode();
}

class Solution {
  public int longestCommonPrefix(int[] arr1, int[] arr2) {
    int ans = 0;
    Trie trie = new Trie();

    for (final int num : arr1)
      trie.insert(Integer.toString(num));

    for (final int num : arr2)
      ans = Math.max(ans, trie.search(Integer.toString(num)));

    return ans;
  }
}

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class TrieNode:
  def __init__(self):
    self.children: dict[str, TrieNode] = {}


class Trie:
  def __init__(self):
    self.root = TrieNode()

  def insert(self, word: str) -> None:
    node: TrieNode = self.root
    for c in word:
      node = node.children.setdefault(c, TrieNode())
    node.isWord = True

  def search(self, word: str) -> int:
    prefixLength = 0
    node = self.root
    for c in word:
      if c not in node.children:
        break
      node = node.children[c]
      prefixLength += 1
    return prefixLength


class Solution:
  def longestCommonPrefix(self, arr1: list[int], arr2: list[int]) -> int:
    trie = Trie()

    for num in arr1:
      trie.insert(str(num))

    return max(trie.search(str(num)) for num in arr2)