Rekonstrukcija (државен '16) za 4/10 (PS. cudno e)

#include <bits/stdc++.h>
using namespace std;

struct p {
    int x = -1;
    int y = -1;
};

int main()
{
//    std::ios::sync_with_stdio(false);
//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);
    int k;
    cin >> k;
    map<int, p> m;
    for (int i = 0; i < k-1; ++i) {
        int a, b;
        cin >> a >> b;
        if (m[a].x == -1) m[a].x = b;
        else m[a].y = b;
        if (m[b].x == -1) m[b].x = a;
        else m[b].y = a;
    }
    vector<int> r[2] = {{0}, {k}};
    //(-1), 0, ...
    //(-1), k, ...
    int prev_r;
    for (int i = 0; i < 2; ++i) {
        prev_r = -1;
        while (true) {
            bool f = 1;
            auto it = m.find(r[i].back());
            if (it != m.end()) {
                if (it->second.x == prev_r) {
                    prev_r = r[i].back();
                    r[i].push_back(it->second.y);
                } else { // y = prev_r
                    prev_r = r[i].back();
                    r[i].push_back(it->second.x);
                }
            } else {
                break;
            }
        }
    }
    for (int i = 0; i < r[0].size()-1; ++i) cout << r[0][i] << " ";
    for (int j = r[1].size()-2; j >= 0; --j) cout << r[1][j] << " "; //j=(size-1)-1
}