Submission #821801

#	Time	Username	Problem	Language	Result	Execution time	Memory
821801		tch1cherin	Tug of War (BOI15_tug)	C++17	100 / 100	486 ms	17604 KiB

tug

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

const int N = 30000 * 20 + 1;

void solve() {
  int n, k;
  cin >> n >> k;
  vector<int> l(2 * n), r(2 * n), s(2 * n);
  vector idx(2, vector<set<int>>(n));
  vector cnt(2, vector<int>(n));
  for (int i = 0; i < 2 * n; i++) {
    cin >> l[i] >> r[i] >> s[i];
    l[i]--, r[i]--;
    idx[0][l[i]].insert(i);
    idx[1][r[i]].insert(i);
    cnt[0][l[i]]++, cnt[1][r[i]]++;
  }
  queue<pair<int, int>> q;
  for (int i = 0; i < n; i++) {
    if (cnt[0][i] <= 1) {
      q.push({i, 0});
    }
    if (cnt[1][i] <= 1) {
      q.push({i, 1});
    }
  }
  vector<bool> deleted(2 * n, false);
  vector used(2, vector<bool>(n, false));
  vector g(2, vector<vector<int>>(2 * n));
  int diff = 0;
  while (!q.empty()) {
    auto [i, t] = q.front();
    q.pop();
    if (cnt[t][i] == 0) {
      cout << "NO\n";
      return;
    }
    int j = *idx[t][i].begin();
    if (t == 0) {
      diff += s[j];
    } else {
      diff -= s[j]; 
    }
    used[t][i] = true;
    deleted[j] = true;
    cnt[0][l[j]]--;
    cnt[1][r[j]]--;
    idx[0][l[j]].erase(j);
    idx[1][r[j]].erase(j);
    if (cnt[0][l[j]] == 1) {
      q.push({l[j], 0});
    }
    if (cnt[1][r[j]] == 1) {
      q.push({r[j], 1});
    }
  }
  for (int i = 0; i < 2 * n; i++) {
    if (!deleted[i]) {
      if (!used[0][l[i]]) {
        g[0][i].push_back(l[i]);
        g[1][l[i]].push_back(i);
      }
      if (!used[1][r[i]]) {
        g[0][i].push_back(r[i] + n);
        g[1][r[i] + n].push_back(i);
      }
    }
  }
  int cost0 = 0;
  vector<int> d;
  int sum = 0;
  for (int i = 0; i < 2 * n; i++) {
    if (!deleted[i]) {
      sum += s[i];
    }
  }
  for (int i = 0; i < 2 * n; i++) {
    if (deleted[i]) {
      continue;
    }
    int j = i, par = -1, step = 0, ss = 0, c0 = 0, c1 = 0;
    bool first = true;
    while (first || j != i || step != 0) {
      if (step == 0) {
        deleted[j] = true;
        if (ss == 0) {
          c0 += s[j];
        } else {
          c1 += s[j];
        }
        ss ^= 1;
      }
      first = false;
      if (g[step][j][0] == par) {
        par = j;
        j = g[step][j][1];
      } else {
        par = j;
        j = g[step][j][0];
      }
      step ^= 1;
    }
    cost0 += c0;
    d.push_back(c1 - c0);
  }
  bitset<N> b;
  b[cost0] = 1;
  for (int v : d) {
    if (v < 0) {
      b |= b >> (-v);
    } else {
      b |= b << v;
    }
  }
  for (int i = 0; i <= sum; i++) {
    int j = sum - i;
    if (b[i] && abs(i - j + diff) <= k) {
      cout << "YES\n";
      return;
    }
  }
  cout << "NO\n";
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  solve();
}

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