Submission #337748

#	Time	Username	Problem	Language	Result	Execution time	Memory
337748		HynDuf	Tug of War (BOI15_tug)	C++11	100 / 100	897 ms	14504 KiB

tug

#include <bits/stdc++.h>
#define F first
#define S second
#define eb emplace_back
#define pb push_back
#define pf push_front
#define all(v) (v).begin(), (v).end()
#define rep(i, l, r) for (int i = (l); i <= (r); i++)
#define Rep(i, r, l) for (int i = (r); i >= (l); i--)
#define DB(X) {cerr << #X << " = " << X << '\n';}
#define DB1(A, _) {cerr << #A << "[" << _ << "] = " << A[_] << '\n';}
#define DB2(A, _, __) {cerr << #A << "[" << _ << "][" << __ << "] = " << A[_][__] << '\n';}
#define DB3(A, _, __, ____) {cerr << #A << "[" << _ << "][" << __ << "][" << ___ << "] = " << A[_][__][___] << '\n';}
#define PR(A, l, r) {cerr << '\n'; rep(_, l, r) DB1(A, _); cerr << '\n';}
#define left ___left
#define right ___right
#define next ___next
#define prev ___prev
#define y1 ___y1
#define y0 ___y0
#define j0 ___j0
#define SZ(x) ((int)(x).size())
using ll = long long;
using ld = long double;
using namespace std;
typedef vector<int> vi;
typedef pair<int, int> ii;
typedef pair<ii, int> iii;
typedef vector<ii> vii;
typedef vector<ll> vl;
const int N = 6e4 + 2, NN = 600002;
int n, cnt[N], K;
struct Tug
{
    int l, r, s;
} tug[N];
set<int> tu[N];
vii g[N];
vi obj;
bool vis[N];
int cur;
void dfs(int u, int r)
{
    cnt[u] = 0;
    for (const ii &v : g[u]) if (!vis[v.S])
    {
        vis[v.S] = 1;
        if (u > n) cur -= tug[v.S].s;
        else cur += tug[v.S].s;
        if (v.F != r) dfs(v.F, r);
    }
}
bitset<NN> dp;
int main()
{
//    freopen("T.in", "r", stdin);
//    freopen("T.out", "w", stdout);
    ios_base::sync_with_stdio(false); cin.tie(nullptr);
    cin >> n >> K;
    rep(i, 1, n << 1)
    {
        int l, r, s;
        cin >> l >> r >> s;
        r += n;
        tug[i] = {l, r, s};
        cnt[l]++, cnt[r]++;
        tu[l].insert(i);
        tu[r].insert(i);
    }
    queue<int> q;
    rep(i, 1, (n << 1)) if (cnt[i] == 0)
    {
        cout << "NO";
        return 0;
    } else if (cnt[i] == 1) q.push(i);
    int ans = 0;
    while (!q.empty())
    {
        int u = q.front();
        q.pop();
        if (cnt[u] == 0)
        {
            cout << "NO";
            return 0;
        }
        assert(cnt[u] == 1);
        assert(SZ(tu[u]) == 1);
        cnt[u] = 0;
        int id = *tu[u].begin();
        int ano = (tug[id].l == u ? tug[id].r : tug[id].l);
        if (--cnt[ano] == 1) q.push(ano);
        if (u > n) ans -= tug[id].s;
        else ans += tug[id].s;
        tu[ano].erase(id);
    }
    rep(u, 1, (n << 1)) if (cnt[u])
    {
        assert(cnt[u] == 2);
        assert(SZ(tu[u]) == 2);
        auto it = tu[u].begin();
        int ano = (tug[*it].l == u ? tug[*it].r : tug[*it].l);
        g[u].eb(ano, *it);
        it++;
        ano = (tug[*it].l == u ? tug[*it].r : tug[*it].l);
        g[u].eb(ano, *it);
    }
    rep(i, 1, (n << 1)) if (cnt[i] == 2)
    {
        cur = 0;
        dfs(i, i);
        obj.eb(abs(cur));
    }
    obj.eb(abs(ans));
    dp[0] = 1;
    int tot = 0;
    for (int v : obj) dp |= dp << v, tot += v;
    rep(i, 0, tot) if (dp[i] && abs(tot - i - i) <= K)
    {
        cout << "YES";
        return 0;
    }
    cout << "NO";
    return 0;
}

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