Submission #127311

#	Time	Username	Problem	Language	Result	Execution time	Memory
127311		srvlt	Fireworks (APIO16_fireworks)	C++14	7 / 100	19 ms	14484 KiB

fireworks

#include <bits/stdc++.h>
#define ll long long
#define db long double
#define pb push_back
#define ppb pop_back
#define fi first
#define se second
#define mp make_pair
#define endl "\n"
#define int long long
using namespace std;

const int N = 3e5 + 3, inf = 1e18;
int n, m;
vector <pair <int, int> > q[N];
vector <int> leaves[N];

void dfs1(int v, int p) {
    for (auto i : q[v]) {
        int to = i.fi, w = i.se;
        if (to != p) {
            dfs1(to, v);
            for (auto j : leaves[to]) {
                leaves[v].pb(j + w);
            }
        }
    }
    if (q[v].size() == 1 && v != 1) {
        leaves[v] = {0};
    }
}

int dfs2(int v, int p, int k) {
    if (q[v].size() == 1 && v != 1) {
        return abs(k);
    }
    int ans = inf;
    for (auto i : leaves[v]) {
        int delta = k - i, res = 0;
        for (auto j : q[v]) {
            int to = j.fi, w = j.se;
            if (to != p) {
                res += dfs2(to, v, k - w - delta);
            }
        }
        ans = min(ans, res + abs(delta));
    }
    return ans;
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin>>n>>m;
    for (int i = 2; i <= n + m; i++) {
        int x, y;
        cin>>x>>y;
        q[x].pb({i, y});
        q[i].pb({x, y});
    }
    dfs1(1, 1);
    for (int i = 1; i <= n + m; i++) {
        leaves[i].pb(0);
    }
    int l = 0, r = 1e9, magic = 31;
    while (magic--) {
        int mid = (l + r) >> 1LL;
        if (dfs2(1, 1, mid) > dfs2(1, 1, mid + 1)) {
            l = mid + 1;
        }   else {
            r = mid;
        }
    }
    cout<<dfs2(1, 1, l);
}

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