Submission #722571

#	Time	Username	Problem	Language	Result	Execution time	Memory
722571		stevancv	Beads and wires (APIO14_beads)	C++14	0 / 100	3 ms	4988 KiB

beads

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sp ' '
#define en '\n'
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
using namespace std;
const int N = 2e5 + 2;
const int inf = 1e9;
vector<pair<int, int>> g[N];
int dp[N][2];
void Dfs(int s, int e, int val) {
    int sum = 0; int mx = -inf;
    for (auto z : g[s]) {
        int u = z.first; int v = z.second;
        if (u == e) continue;
        Dfs(u, s, v);
        sum += max(dp[u][0], dp[u][1]);
        smax(mx, dp[u][0] + v + val - max(dp[u][0], dp[u][1]));
    }
    dp[s][0] = sum; dp[s][1] = sum + mx;
}
int sol, up[N][2];
void Dfs1(int s, int e, int val) {
    smax(sol, max(up[s][0], up[s][1]) + dp[s][0]);
    int x, y;
    x = y = -inf;
    for (auto z : g[s]) {
        int u = z.first; int v = z.second;
        if (u == e) continue;
        int o = dp[u][0] + v - max(dp[u][0], dp[u][1]);
        if (o > x) y = x, x = o;
        else if (o > y) y = o;
    }
    for (auto z : g[s]) {
        int u = z.first; int v = z.second;
        if (u == e) continue;
        int uk = dp[s][0] - max(dp[u][0], dp[u][1]);
        if (s > 1) up[u][1] = up[u][0] + val + v + uk;
        int o = dp[u][0] + v - max(dp[u][0], dp[u][1]);
        int kolko = x;
        if (o == x) kolko = y;
        smax(up[u][1], v + uk + kolko + max(up[s][0], up[s][1]));
        up[u][0] = max(up[s][0], up[s][1]) + uk;
        Dfs1(u, s, v);
    }
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n; cin >> n;
    for (int i = 0; i < n - 1; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        g[u].push_back({v, w});
        g[v].push_back({u, w});
    }
    Dfs(1, 0, 0);
    Dfs1(1, 0, 0);
    cout << sol << en;
    return 0;
}

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