Submission #1218684

#	Time	Username	Problem	Language	Result	Execution time	Memory
1218684		BigBadBully	Tug of War (BOI15_tug)	C++20	100 / 100	1825 ms	16264 KiB

tug

#include <bits/stdc++.h>
#define int long long
#define pii pair<int, int>
#define ff first
#define ss second
using namespace std;
bitset<2*20*30000+1> mile;
signed main()
{
    int n, k;
    cin >> n >> k;
    vector<multiset<pii>> graph(2*n);
    for (int i = 0; i < 2 * n; i++)
    {
        int a, b, c;
        cin >> a >> b >> c;
        graph[--a].insert({--b + n, c});
        graph[b + n].insert({a, c});
    }
    set<pii> degs;
    int sum = 0;
    for (int i = 0; i < 2*n; i++)
        degs.insert({graph[i].size(), i});
    vector<int> vis(2*n,0);
    auto brisi = [&](int i)
    {
        vis[i] = 1;
        auto x = *graph[i].begin();
        sum += x.ss * (i >= n ? -1 : 1);
        degs.erase(degs.find({graph[x.ff].size(), x.ff}));
        graph[x.ff].erase({i, x.ss});
        degs.erase(degs.find({1, i}));
        degs.insert({graph[x.ff].size(), x.ff});
    };
    while ((*degs.begin()).ff < 2)
    {
        auto x = *degs.begin();
        if (x.ff == 0)
        {
            cout << "NO\n";
            return 0;
        }
        brisi(x.ss);
    }
    if ((*degs.rbegin()).ff > 2)
    {
        cout << "NO\n";
        return 0;
    }
    int ini = 0;
    vector<int> cyc;
    for (int i = 0; i < 2*n; i++)
    {
        if (!vis[i])
        {
            int idx = cyc.size();
            cyc.push_back(0);
            int cur = i;
            int prev = i;
            while(!vis[cur])
            {
                vis[cur] = 1;
                auto x = *graph[cur].begin();
                if (x.ff == prev)
                    x = *++graph[cur].begin();
                prev = cur;
                cyc[idx]+=(x.ff>=n?-1:1)*x.ss;
                cur = x.ff;

            }
            //ini+=-abs(cyc[idx]);
        }
    }
    
    const int hf = 20*30000;
    mile[sum+hf] = 1;
    for (auto x : cyc)
    {
        auto prev = mile;
        mile=prev<<abs(x);
        mile|=prev>>abs(x);
    }
    bool ther = 0;
    for (int i = hf-k; i <= hf+k; i++)
        ther|=mile[i];
    cout << (ther?"YES\n":"NO\n");
}

• Subtask 1: 18 / 18
• Subtask 2: 30 / 30
• Subtask 3: 23 / 23
• Subtask 4: 29 / 29