Submission #1256387

#	Time	Username	Problem	Language	Result	Execution time	Memory
1256387		madamadam3	Souvenirs (IOI25_souvenirs)	C++20	100 / 100	12 ms	420 KiB

souvenirs

#include "souvenirs.h"
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
using vi = vector<int>;
using vvi = vector<vi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using pi = pair<int, int>;

#define FOR(i, a, b) for (int i = a; i < b; i++)
#define ROF(i, a, b) for (int i = a; i >= b; i--)
#define each(a, x) for (auto &a : x)
#define all(x) (x).begin(), (x).end()
#define bg(x) (x).begin()
#define en(x) (x).end()
#define rev(x) reverse(all(x))
#define sz(x) int((x).size())
#define srt(x) sort(all(x))
#define cnt(a, x) count(all(x), a)
#define trace(x) each(a, (x)) cerr << a << " "
#define mp make_pair
#define pb push_back
#define lb lower_bound
#define ub upper_bound

struct DSU {
  int n; vi par, siz;

  DSU() {};
  DSU(int N) {
    n = N; par.resize(n); siz.assign(n, 1);
    iota(all(par), 0);
  }

  int find(int v) {
    if (par[v] == v) return v;
    return par[v] = find(par[v]);
  }

  void unite(int a, int b) {
    a = find(a); b = find(b);
    if (a != b) {
      if (siz[a] < siz[b]) swap(a, b);
      par[b] = a;
      siz[a] += siz[b];
    }
  }
};

using R = pair<vi, ll>;
struct txn {ll paid; R res;};
const ll INF = 4e18;

int n;
vi bought; vl price, low, high;

R transact(ll money) {
  auto res = transaction(money);
  for (auto &el : res.first) {
    bought[el]++;
  }
  
  // cerr << "Money: " << money << " Received: ["; for (auto &el : res.first) cerr << " " << el; cerr << " ] Change: " << res.second << "\n";
  return res;
}

// find the minimum value the most expensive item must have such that the other values can satisfy the conditions and be >=  paid
ll find_min(ll paid, int received) {
  ll lo = 1, hi = 1e15;

  while (lo < hi) {
    ll mid = lo + (hi - lo) / 2;

    bool check = true;
    ll tl = mid; for (int i = 1; i < received; i++) {
      if (mid - i <= 0) {
        check = false;
        break;
      }
      tl += (mid - i);
    }
    
    check = check && tl >= paid;

    if (check) {
      hi = mid;
    } else {
      lo = mid + 1;
    }
  }

  return lo;
}

// o1: if we continually find the smallest possible number which p[x] must be, we eventually reach n-1
// o2: the original returned list goes down in a daisy chain and determines p[1]

bool can_resolve(vi ret) {
  bool can = true;
  for (auto &el : ret) can = can && price[el] != -1;
  return can;
}

int id = 0;
void dfs(ll paid, int pid) { // returns 
  int myid = id++;
  // cerr << myid << " called by " << pid << "\n";
  auto r = transact(paid);
  ll used = paid - r.second;

  if (sz(r.first) == 1) {
    price[r.first[0]] = used;
    if (r.first[0] != n-1) dfs(used - 1, myid); 
    return;
  }

  while (sz(r.first) > 1) {
    vi nf = {r.first[0]};
    for (int i = 1; i < sz(r.first); i++) {
      if (price[r.first[i]] == -1) {
        nf.push_back(r.first[i]);
        continue;
      }

      used -= price[r.first[i]];
    }

    r.first = nf;
    if (r.first.size() == 1) break;
    // cerr << myid << " open "; trace(r.first); cerr << "\n";

    ll np = find_min(used, r.first.size()) - 1;
    dfs(np, myid);
  }

  price[r.first[0]] = used;
  // cerr << "Aim: " << r.first[0] + 1 << " Price: " << price[r.first[0] + 1] << "\n";
  if (price[r.first[0] + 1] == -1) dfs(used - 1, myid);
  return;
}

void buy_souvenirs(int N, ll P0) {
  n = N;
  bought.assign(n, 0); price.assign(n, -1);
  price[0] = P0;

  FOR(i, 1, n) {
    if (price[i] != -1) continue;
    // cerr << "No price for " << i << " using parent " << i - 1 << "'s price -1 of " << price[i-1] - 1 << "\n";
    ll paid = price[i-1] - 1;
    dfs(paid, -1);
  }

  FOR(i, 0, n) {
    // cerr << price[i] << " ";
    if (price[i] == -1) continue;
    while (bought[i] < i) {
      transact(price[i]);
    }
  }
  // cerr << "\n";
}

• Subtask 0: 0 / 0
• Subtask 1: 4 / 4
• Subtask 2: 3 / 3
• Subtask 3: 14 / 14
• Subtask 4: 18 / 18
• Subtask 5: 28 / 28
• Subtask 6: 33 / 33