Submission #752955

#	Time	Username	Problem	Language	Result	Execution time	Memory
752955		benjaminkleyn	Fireworks (APIO16_fireworks)	C++17	7 / 100	6 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, lo, hi;
};

pair<ll,ll> dp(int u, ll dist=0, ll len=-1)
{
    if (u > n)
        return {0, 0};

    ll res = 0;
    vector<ll> T;
    ll min_val = 0;
    for (auto [v, l] : g[u])
    {
        auto [t, d] = dp(v, dist + l, len);
        res += t;
        T.push_back(l +  d);
        min_val = max(min_val, d);
    }
    sort(T.begin(), T.end());

    ll best = T[(T.size() - 1) / 2];
    if (len != -1)
    {
        if (dist + best <= len && len <= dist + T[T.size()/2])
            best = len - dist;
        else if (abs(dist + best - len) > abs(dist + T[T.size()/2] - len))
            best = T[T.size()/2];
    }
    if (min_val >= best)
        best = min_val;
    for (ll x : T)
        res += abs(best - x);
    return {res, best};
}

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, 0, dp(1).second).first << '\n';

    return 0;
}

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