Vi村さんの重複キー検索の問題（C++17）

Makefile

map_key: map_key.cpp
	$(CXX) -o $@ -std=gnu++17 -Wall -Wpedantic -g $^

map_key.cpp

#include <iostream>
#include <string>
#include <sstream>
#include <map>
#include <vector>

struct Hoge {
  std::string hoge1;
  std::string hoge2;
  std::string hoge3;
};

using StringHogeMap = std::map<std::string, Hoge>;
using StringStringHogeMap = std::map<std::string, StringHogeMap>;

// テスト用のmapを用意する
StringStringHogeMap setup_map();
// mapの内容を出力する
void print_map(const StringStringHogeMap& m);

int main() {
  StringStringHogeMap m = setup_map();

  std::cout << "[Map]" << std::endl;
  print_map(m);
  std::cout << std::endl;

  using StringVector = std::vector<std::string>;
  // 「key => keyを格納しているnameのvector」のmap
  std::map<std::string, StringVector> key_names;

  for (const auto& [name, key_value] : m) {
    for (const auto& [key, _value] : key_value) {
      auto it = key_names.find(key);
      if (it == key_names.end()) {
        // 初めて発見したkeyの場合、nameを格納するvectorを作る
        key_names[key] = StringVector{};
      }

      // vectorにnameを追加する
      key_names[key].push_back(name);
    }
  }

  std::cout << "[Duplication]" << std::endl;

  for (const auto& [key, names] : key_names) {
    if (names.size() > 1) {
      // namesの要素が複数ある => 複数のnameに共通のkeyが存在する

      std::cout << key << " < " << names[0];

      for (auto it = names.cbegin() + 1; it != names.cend(); ++it) {
        std::cout << ", " << *it;
      }

      std::cout << std::endl;
    }
  }
}

// テスト用のmapを用意する
StringStringHogeMap setup_map() {
  StringStringHogeMap m{};

  std::string name0{"name0"};
  m[name0] = StringHogeMap{};

  // "name0" に0-9の要素を挿入する
  for (int i = 0; i < 10; ++i) {
    std::stringstream ss_key;
    ss_key << "key" << i;
    std::string key = ss_key.str();

    std::stringstream ss_value;
    ss_value << "hoge" << i;
    std::string value = ss_value.str();

    m[name0][key] = Hoge{value, value, value};
  }

  std::string name1{"name1"};

  // キーが重複している要素を挿入する
  m[name1] = StringHogeMap{
    {std::string{"key0"}, {std::string{"hoge0"}, std::string{"hoge0"}, std::string{"hoge0"}}},
    {std::string{"key9"}, {std::string{"hoge9"}, std::string{"hoge9"}, std::string{"hoge9"}}},
  };

  // "name1" に10-19の要素を挿入する
  for (int i = 10; i < 20; ++i) {
    std::stringstream ss_key;
    ss_key << "key" << i;
    std::string key = ss_key.str();

    std::stringstream ss_value;
    ss_value << "hoge" << i;
    std::string value = ss_value.str();

    m[name1][key] = Hoge{value, value, value};
  }

  return m;
}

// mapの内容を出力する
void print_map(const StringStringHogeMap& m) {
  for (const auto& [name, key_value] : m) {
    std::cout << name << ":" << std::endl;

    for (const auto& [key, value] : key_value) {
      std::cout << "  " << key << ": {";
      std::cout << value.hoge1 << ", " << value.hoge2 << ", " << value.hoge3 << "}";
      std::cout << std::endl;
    }
  }
}

output.txt

[Map]
name0:
  key0: {hoge0, hoge0, hoge0}
  key1: {hoge1, hoge1, hoge1}
  key2: {hoge2, hoge2, hoge2}
  key3: {hoge3, hoge3, hoge3}
  key4: {hoge4, hoge4, hoge4}
  key5: {hoge5, hoge5, hoge5}
  key6: {hoge6, hoge6, hoge6}
  key7: {hoge7, hoge7, hoge7}
  key8: {hoge8, hoge8, hoge8}
  key9: {hoge9, hoge9, hoge9}
name1:
  key0: {hoge0, hoge0, hoge0}
  key10: {hoge10, hoge10, hoge10}
  key11: {hoge11, hoge11, hoge11}
  key12: {hoge12, hoge12, hoge12}
  key13: {hoge13, hoge13, hoge13}
  key14: {hoge14, hoge14, hoge14}
  key15: {hoge15, hoge15, hoge15}
  key16: {hoge16, hoge16, hoge16}
  key17: {hoge17, hoge17, hoge17}
  key18: {hoge18, hoge18, hoge18}
  key19: {hoge19, hoge19, hoge19}
  key9: {hoge9, hoge9, hoge9}

[Duplication]
key0 < name0, name1
key9 < name0, name1