제출 #1163778

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1163778		byunjaewoo	구슬과 끈 (APIO14_beads)	C++20	0 / 100	2 ms	4932 KiB

beads

#include <bits/stdc++.h>
#define int long long
using namespace std;

const int N=200010, INF=1e15;
int n, pw[N], dp[2][N], ep[N];
vector<pair<int, int>> adj[N];

void dfs(int curr, int prev) {
    int sum=0, mx=-INF, mx1=-INF, mx2=-INF, mx3=-INF;
    vector<int> vec;
    for(auto [next, w]:adj[curr]) if(next!=prev) {
        pw[next]=w, dfs(next, curr);
        dp[0][curr]+=max({dp[0][next], dp[1][next], ep[next]});
        sum+=max(dp[0][next], ep[next]);
        if(max(dp[0][next], dp[1][next])>=ep[next]) mx=max(mx, w);
        else mx=max(mx, max(dp[0][next], dp[1][next])+w-ep[next]);
        if(dp[0][next]>=ep[next]) {
            if(mx1<w) mx2=mx1, mx1=w;
            else if(mx2<w) mx2=w;
        }
        else {
            if(mx1<dp[0][next]+w-ep[next]) mx2=mx1, mx1=dp[0][next]+w-ep[next];
            else if(mx2<dp[0][next]+w-ep[next]) mx2=dp[0][next]+w-ep[next];
        }
        vec.push_back(mx1);
    }
    dp[1][curr]=sum+mx1+mx2;
    reverse(adj[curr].begin(), adj[curr].end());
    int p=(int)vec.size()-1;
    for(auto [next, w]:adj[curr]) if(next!=prev) {
        dp[1][curr]=max(dp[1][curr], sum-max(dp[0][next], ep[next])+dp[1][next]+max(mx3, p?vec[--p]:-INF));
        if(dp[0][next]>=ep[next]) mx3=max(mx3, w);
        else mx3=max(mx3, dp[0][next]+w-ep[next]);
    }
    ep[curr]=dp[0][curr]+mx+pw[curr];
}

signed main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    cin>>n;
    for(int i=1; i<n; i++) {
        int u, v, w; cin>>u>>v>>w;
        adj[u].push_back({v, w}), adj[v].push_back({u, w});
    }
    fill(dp[1]+1, dp[1]+n+1, -INF), fill(ep+1, ep+n+1, -INF);
    dfs(1, 0);
    cout<<max(dp[0][1], dp[1][1]);
    return 0;
}

• Subtask 1: 0 / 13
• Subtask 2: 0 / 15
• Subtask 3: 0 / 29
• Subtask 4: 0 / 43