Submission #389163

#	Time	Username	Problem	Language	Result	Execution time	Memory
389163		phathnv	Beads and wires (APIO14_beads)	C++11	100 / 100	327 ms	35484 KiB

beads

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

typedef long long ll;

const int N = 2e5 + 7;
const int INF = 1e9 + 7;

struct Edge{
    int v, c;
    Edge(int _v, int _c){
        v = _v;
        c = _c;
    }
};

int n, down[N][2], up[N][2];
vector<Edge> adj[N];

void Dfs(int u, int p){
    down[u][0] = 0;
    down[u][1] = -INF;
    for(Edge e : adj[u]){
        int v = e.v;
        int c = e.c;
        if (v == p)
            continue;
        Dfs(v, u);
        down[u][1] = max(down[u][1] + max(down[v][0], down[v][1] + c), down[u][0] + down[v][0] + c);
        down[u][0] += max(down[v][0], down[v][1] + c);
    }
}

void Dfs2(int u, int p){
    if (p == -1){
        up[u][0] = 0;
        up[u][1] = -INF;
    }
    int sum = up[u][0];
    multiset<int> s;
    s.insert(up[u][1] - up[u][0]);
    for(Edge e : adj[u]){
        int v = e.v;
        int c = e.c;
        if (v == p)
            continue;
        sum += max(down[v][0], down[v][1] + c);
        s.insert(down[v][0] + c - max(down[v][0], down[v][1] + c));
    }
    for(Edge e : adj[u]){
        int v = e.v;
        int c = e.c;
        if (v == p)
            continue;
        sum -= max(down[v][0], down[v][1] + c);
        s.erase(s.find(down[v][0] + c - max(down[v][0], down[v][1] + c)));
        up[v][0] = sum + max(0, *(--s.end()) + c);
        up[v][1] = sum + c;
        s.insert(down[v][0] + c - max(down[v][0], down[v][1] + c));
        sum += max(down[v][0], down[v][1] + c);
    }

    for(Edge e : adj[u]){
        int v = e.v;
        if (v == p)
            continue;
        Dfs2(v, u);
    }
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    cin >> n;
    for(int i = 1; i < n; i++){
        int u, v, c;
        cin >> u >> v >> c;
        adj[u].push_back(Edge(v, c));
        adj[v].push_back(Edge(u, c));
    }

    Dfs(1, -1);
    Dfs2(1, -1);
    int res = 0;
    for(int i = 1; i <= n; i++)
        res = max(res, up[i][0] + down[i][0]);
    cout << res;

    return 0;
}

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