SDA - 2018 2019 - test5 - task 2

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>
#include <queue>

using namespace std;

unordered_map<int, unordered_set<int>> graph;
unordered_map<int, int> path;

void bfs(){
    queue<int> next;
    next.push(0);
    path[0] = 0;
    while(!next.empty()) {
        int current = next.front();
        next.pop();
        for(auto i : graph[current]){
            if(path.count(i) == 0){
                path[i] = path[current] + 1;
                next.push(i);
            }
        }
    }
}

int main() {
    int k, a, b;
    cin >> k;
    for(int i = 0; i < k; i++){
        cin >> a >> b;
        graph[a].insert(b);
        graph[b].insert(a);
    }
    bfs();

    int sum = 0;

    for(auto i : path)
        sum += i.second;

    cout << sum;



    return 0;
}