Submission #1109133

#	Time	Username	Problem	Language	Result	Execution time	Memory
1109133		codexistent	Tug of War (BOI15_tug)	C++14	100 / 100	584 ms	35320 KiB

tug

#include <bits/stdc++.h>
using namespace std;
#define MAXN 600005
#define FOR(i, a, b) for(int i = a; i <= b; i++)

multiset<pair<int, int>> e[MAXN];
bool v[MAXN];
int n, k, r = 0, r2 = 0;
bitset<MAXN> bs;

void dfs(int node){
    v[node] = true;
    if(!e[node].size()) return;
    int nxt, cost;
    tie(nxt, cost) = *e[node].begin();

    r += cost;
    if(!v[nxt]){
        e[nxt].erase(e[nxt].find({node, -cost}));
        e[node].clear();
        dfs(nxt);
    }
}

int main(){
    cin >> n >> k;
    FOR(i, 1, 2 * n){
        int l, r, s;
        cin >> l >> r >> s;

        e[l].insert({n + r, s}), e[n + r].insert({l, -s});
    }

    queue<int> q;
    FOR(i, 1, 2 * n) {
        if(e[i].size() == 1) q.push(i);
        if(e[i].size() == 0) return cout << "NO" << endl, 0;
    }

    while(q.size()){
        int qi = q.front(); q.pop();
        if(e[qi].size() == 0) return cout << "NO" << endl, 0;
        
        int nxt, cost;
        tie(nxt, cost) = *e[qi].begin();
        r += cost;

        e[qi].clear();
        e[nxt].erase(e[nxt].find({qi, -cost}));
        if(e[nxt].size() == 1) q.push(nxt);
    }

    vector<int> items;
    if(r) items.push_back(abs(r));
    FOR(i, 1, 2 * n){
        if(!v[i] && e[i].size()){
            r = 0;
            e[i].erase(e[i].begin());

            dfs(i);
            if(r) items.push_back(abs(r));
        }
    }
    r2 = accumulate(items.begin(), items.end(), 0);

    bs[0] = 1;
    for(int i : items) bs |= bs << i;
    FOR(i, 0, r2){
        if(bs[i] && abs(2 * i - r2) <= k) return cout << "YES" << endl, 0; 
    }

    return cout << "NO" << endl, 0;
}

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