[uva] 11396 – claw decomposition

#include <queue>
#include <vector>
#ifdef LOCAL
#include "stloutput.h"
#endif
#define INF 1000000000

using namespace std;

int () {
    int V;
    while (cin >> V, V) {
        int a, b;
        vector<vector<int>> g(V);
        while (cin >> a >> b, a | b) {
            a--, b--;
            g[a].push_back(b);
            g[b].push_back(a);
        }
        vector<int> color(V, -1);
        queue<int> q;
        q.push(0);
        color[0] = 0;
        bool bi = true;
        while (!q.empty() && bi) {
            int tmp = q.front();
            q.pop();
            for (auto i : g[tmp]) {
                if (color[i] == -1) {
                    color[i] = 1 - color[tmp];
                    q.push(i);
                } else if (color[i] == color[tmp]) {
                    bi = false;
                    break;
                }
            }
        }
        bi ? cout << "YES" << endl : cout << "NO" << endl;
    }
}