Submission #198285

#	Time	Username	Problem	Language	Result	Execution time	Memory
198285		parsa_mobed	Beads and wires (APIO14_beads)	C++14	100 / 100	354 ms	23920 KiB

beads

#include <bits/stdc++.h>

using namespace std;
const int N = 2e5 + 10, inf = 1e9 + 5;
int dp[N][2], dpU[N][2], par[N], mx[N], E[N][3], MX1[N], MX2[N];
vector <int> g[N];

inline int adj(int v, int i) {return (v^E[i][0]^E[i][1]);}

void dfs(int v)
{
    for (int i : g[v]) if (adj(v, i) != par[v]) {
        par[adj(v, i)] = v;
        dfs(adj(v, i));
        mx[adj(v, i)] = max(dp[adj(v, i)][1] + E[i][2], dp[adj(v, i)][0]);
        dp[v][0] += mx[adj(v, i)];
    }
    for (int i : g[v]) if (adj(v, i) != par[v]) {
        if (dp[adj(v, i)][0] - mx[adj(v, i)] + E[i][2] > MX1[v])
            MX2[v] = MX1[v], MX1[v] = dp[adj(v, i)][0] - mx[adj(v, i)] + E[i][2];
        else if (dp[adj(v, i)][0] - mx[adj(v, i)] + E[i][2] > MX2[v])
            MX2[v] = dp[adj(v, i)][0] - mx[adj(v, i)] + E[i][2];
        dp[v][1] = max(dp[v][1], dp[v][0] - mx[adj(v, i)] + dp[adj(v, i)][0] + E[i][2]);
    }
}

void dfsUp(int v, int w = 0)
{
    int p = par[v];
    if (p != 0) {
        int x = dpU[p][0] + dp[p][0] - mx[v] + w;
        dpU[v][0] = x - w, dpU[v][1] = x;;
        if (MX1[p] != dp[v][0] - mx[v] + w) dpU[v][0] = max(dpU[v][0], MX1[p] + x);
        else dpU[v][0] = max(dpU[v][0], MX2[p] + x);
        dpU[v][0] = max(dpU[v][0], dpU[p][1] - dpU[p][0] + x);
    }
    for (int i : g[v]) if (adj(v, i) != p) dfsUp(adj(v, i), E[i][2]);
}

int32_t main()
{
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int n; cin >> n;
    for (int i = 0; i < n - 1; i++) {
        cin >> E[i][0] >> E[i][1] >> E[i][2];
        g[E[i][0]].push_back(i);
        g[E[i][1]].push_back(i);
    }
    for (int i = 1; i <= n; i++) MX1[i] = MX2[i] = dp[i][1] = dpU[i][1] = -inf;
    dfs(1), dfsUp(1);
    int ans = 0;
    for (int i = 1; i <= n; i++) ans = max(ans, dp[i][0] + dpU[i][0]);
    cout << ans << "\n";

    return 0;
}

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