Submission #469921

#	Time	Username	Problem	Language	Result	Execution time	Memory
469921		Killer2501	Beads and wires (APIO14_beads)	C++14	100 / 100	181 ms	25292 KiB

beads

#include <bits/stdc++.h>
#define ll int
#define pll pair<ll, ll>
#define pb push_back
#define fi first
#define se second
using namespace std;
const int N = 3e5 + 5;
const ll mod = 1e9 + 7;
ll n, m, a[N], b[N], dp[N], gp[N], tong;
vector<pll> adj[N];
void dfs(ll u, ll p, ll s)
{
    ll sum = 0;
    ll mx1 = -mod, mx2 = -mod;
    for (pll v : adj[u])
    {
        if (v.se == p)
            continue;
        dfs(v.se, u, v.fi);
        sum += max(dp[v.se], gp[v.se]);
        int val = dp[v.se] - max(dp[v.se], gp[v.se]) + v.fi;
        if (mx1 < val)
        {
            mx2 = mx1;
            mx1 = val;
        }
        else if (mx2 < val)
            mx2 = val;
    }
    dp[u] = sum;
    a[u] = sum;
    for (pll v : adj[u])
    {
        if (v.se == p)
            continue;
        int val = dp[u] - max(dp[v.se], gp[v.se]);
        gp[u] = max(gp[u], dp[v.se] + val + v.fi + s);
        int mx = v.fi + dp[v.se] - max(dp[v.se], gp[v.se]);
        if (mx == mx1)
            mx = mx2;
        else
            mx = mx1;
        a[u] = max(a[u], a[v.se] + val + v.fi + mx);
        a[u] = max(a[u], a[v.se] + val);
        for (pll z : adj[v.se])
        {
            if (z.se == u)
                continue;
            int valz = dp[v.se] - max(dp[z.se], gp[z.se]);
            a[u] = max(a[u], val + valz + v.fi + z.fi + a[z.se]);
        }
    }
}
void sol()
{
    cin >> n;
    for (int i = 1; i < n; i++)
    {
        ll x, y, w;
        cin >> x >> y >> w;
        adj[x].pb({w, y});
        adj[y].pb({w, x});
    }
    dfs(1, 0, 0);
    cout << a[1];
}
int main()
{
    cin.tie(0);
    cout.tie(0);
    ios_base::sync_with_stdio(0);
    int test = 1;
    //cin >> test;
    while (test-- > 0)
        sol();
    return 0;
}
/*
10
4 10 2
1 2 21
1 3 13
6 7 1
7 9 5
2 4 3
2 5 8
1 6 55
6 8 34
*/
// ctrl + F8 = compile
// ctrl + F9 = run

• Subtask 1: 13 / 13
• Subtask 2: 15 / 15
• Subtask 3: 29 / 29
• Subtask 4: 43 / 43