Submission #752974

#	Time	Username	Problem	Language	Result	Execution time	Memory
752974		benjaminkleyn	Fireworks (APIO16_fireworks)	C++17	7 / 100	4 ms	7380 KiB

fireworks

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

const int MAX = 300010;
int n, m;
int p[2 * MAX]; 
ll c[2 * MAX];
vector<pair<int, ll>> g[MAX];

struct state
{
    ll cost, dist, free_increase;
};

state dp(int u)
{
    if (u > n)
        return {0, 0, 0};

    ll res = 0;
    vector<state> T;
    ll min_val = 0;
    ll free_increase = LLONG_MAX;
    for (auto [v, l] : g[u])
    {
        auto [t, d, free] = dp(v);
        res += t;
        T.push_back({l, d, free});
        free_increase = min(free_increase, free);
        min_val = max(min_val, d);
    }
    sort(T.begin(), T.end(), [] (const state &A, const state &B) {return A.cost + A.dist < B.cost + B.dist;});
    for (int i = 0; i < T.size() / 2; i++)
    {
        ll inc = min(T[i].free_increase, T[T.size()/2].cost + T[T.size()/2].dist - T[i].cost - T[i].dist);
        T[i].dist += inc;
        T[i].free_increase -= inc;
        free_increase = min(free_increase, T[i].free_increase);
    }

    ll best = T[(T.size()-1)/2].cost + T[(T.size()-1)/2].dist, free = T[T.size()/2].cost + T[T.size()/2].dist - T[(T.size()-1)/2].cost - T[(T.size()-1)/2].dist;
    if (min_val >= T[T.size()/2].cost + T[T.size()/2].dist)
        best = min_val, free = 0;
    else if (min_val >= best)
        best = min_val, free = T[T.size()/2].cost + T[T.size()/2].dist - min_val;
    for (state x : T)
        res += abs(best - x.cost - x.dist);
    return {res, best, free_increase + free};
}

int main()
{
    cin.tie(0)->sync_with_stdio(0);

    cin >> n >> m;
    p[1] = -1, c[1] = 0;
    for (int i = 2; i <= n + m; i++)
    {
        cin >> p[i] >> c[i];
        g[p[i]].push_back({i, c[i]});
    }

    cout << dp(1).cost << '\n';

    return 0;
}

Compilation message (stderr)

fireworks.cpp: In function 'state dp(int)':
fireworks.cpp:34:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<state>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   34 |     for (int i = 0; i < T.size() / 2; i++)
      |                     ~~^~~~~~~~~~~~~~

• Subtask 1: 7 / 7
• Subtask 2: 0 / 19
• Subtask 3: 0 / 29
• Subtask 4: 0 / 45