поиск в ширину

#include <iostream>
#include <queue>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
 
using std::cout;
using std::endl;
 
bool is_seller(const std::string& name)
{
    return name.back() == 'm';
}
 
template <typename T>
bool search(const T& name, const std::unordered_map<T, std::vector<T>>& graph)
{
    std::queue<T> search_queue;
    std::unordered_set<T> searched;
 
    // add all friends to search queue
    for (auto&& friend_name : graph.find(name)->second)
        search_queue.push(friend_name);
 
    while (!search_queue.empty()) {
        T& person = search_queue.front();
        search_queue.pop();
 
        // only search this person if you haven't already searched them.
        if (searched.find(person) == searched.end()) {
            if (is_seller(person)) {
                cout << person << " is a mango seller!" << endl;
                return true;
            }
 
            // add all friends of a person to search queue
            for (auto&& friend_name : graph.find(person)->second)
                search_queue.push(friend_name);
 
            // mark this person as searched
            searched.insert(person);
        }
    }
 
    return false;
}
 
int main()
{
    std::unordered_map<std::string, std::vector<std::string>> graph;
    graph.insert({ "you", { "alice", "bob", "claire" } });
    graph.insert({ "bob", { "anuj", "peggy" } });
    graph.insert({ "alice", { "peggy" } });
    graph.insert({ "claire", { "thom", "jonny" } });
    graph.insert({ "anuj", {} });
    graph.insert({ "peggy", {} });
    graph.insert({ "thom", {} });
    graph.insert({ "jonny", {} });
 
    std::string name = "you";
    bool result = search(name, graph);
    cout << "Found mango seller: " << result << endl;
}

auto it = graph.find(name);
if (it != graph.end())
    for (auto &friend_name : it->second)
        search_queue.push(friend_name);