main函数

#include <iostream>
#include <string>
#include <strings.h>
#include <vector>
using namespace std;

int main(void) {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  Trie trie(1024);
  for (int i = 0; i < n; ++i) {
    string oper, str;
    cin >> oper >> str;
    if (oper == "I") {
      trie.insert(str);
    } else if (oper == "Q") {
      cout << trie.count(str) << "\n";
    }
  }
  return 0;
}

Trie树

class Trie {
  class TrieNode {
   public:
    explicit TrieNode() : cnt(0) { bzero(children, sizeof(int) * CHILDREN_SIZE); }
    static constexpr int CHILDREN_SIZE = 26;
    inline int &operator[](unsigned char ch) { return children[ch - 'a']; }
    inline int operator[](unsigned char ch) const { return children[ch - 'a']; }
    int cnt;

   private:
    int children[CHILDREN_SIZE];
  };

 public:
  explicit Trie(int capacity = 64) {
    nodeVec.reserve(capacity);
    nodeVec.emplace_back();
  }
  void insert(const string &str) {
    int i = 0;
    for (const unsigned char ch : str) {
      int &child = nodeVec[i][ch];
      if (!child) {
        child = nodeSize();
        nodeVec.emplace_back();
      }
      i = nodeVec[i][ch];
    }
    ++nodeVec[i].cnt;
  }
  int count(const string &str) const {
    int i = 0;
    for (const unsigned char ch : str) {
      i = nodeVec[i][ch];
      if (!i) {
        return 0;
      }
    }
    return nodeVec[i].cnt;
  }

 private:
  inline int nodeSize() const { return nodeVec.size(); }
  vector<TrieNode> nodeVec;
};

constexpr int Trie::TrieNode::CHILDREN_SIZE;