Submission #731125

#	Time	Username	Problem	Language	Result	Execution time	Memory
731125		stevancv	Cat Exercise (JOI23_ho_t4)	C++14	100 / 100	379 ms	58076 KiB

Main

#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 = 2e9 + 2;
int p[N], inv[N];
int par[N][18], in[N], out[N], dep[N], tsz;
vector<int> g[N];
vector<array<int, 2>> ng[N];
void Dfs(int s, int e) {
    in[s] = ++tsz;
    par[s][0] = e;
    for (int i = 1; i < 18; i++) par[s][i] = par[par[s][i - 1]][i - 1];
    for (int u : g[s]) {
        if (u == e) continue;
        dep[u] = dep[s] + 1;
        Dfs(u, s);
    }
    out[s] = tsz;
}
bool Ancestor(int u, int v) {
    return in[u] <= in[v] && out[v] <= out[u];
}
int Lca(int u, int v) {
    if (Ancestor(u, v)) return u;
    if (Ancestor(v, u)) return v;
    for (int i = 17; i >= 0; i--) {
        if (par[u][i] && !Ancestor(par[u][i], v)) u = par[u][i];
    }
    return par[u][0];
}
struct Dsu {
    int link[N], mx[N];
    void Init(int n) {
        for (int i = 1; i <= n; i++) {
            link[i] = i;
            mx[i] = p[i];
        }
    }
    int Find(int x) {
        if (x == link[x]) return x;
        return link[x] = Find(link[x]);
    }
    void Unite(int x, int y) {
        x = Find(x); y = Find(y);
        if (mx[x] < mx[y]) swap(x, y);
        link[y] = x;
    }
}dsu;
ll Dfs1(int s, int e) {
    ll ret = 0;
    for (auto u : ng[s]) {
        if (u[0] == e) continue;
        smax(ret, Dfs1(u[0], s) + u[1]);
    }
    return ret;
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n; cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> p[i];
        inv[p[i]] = i;
    }
    vector<array<int, 3>> e(n - 1);
    for (int i = 0; i < n - 1; i++) {
        cin >> e[i][1] >> e[i][2];
        e[i][0] = max(p[e[i][1]], p[e[i][2]]);
        g[e[i][1]].push_back(e[i][2]);
        g[e[i][2]].push_back(e[i][1]);
    }
    Dfs(1, 0);
    sort(e.begin(), e.end());
    dsu.Init(n);
    for (auto u : e) {
        int x = dsu.Find(u[1]);
        int y = dsu.Find(u[2]);
        x = inv[dsu.mx[x]];
        y = inv[dsu.mx[y]];
        dsu.Unite(x, y);
        int d = dep[x] + dep[y] - 2 * dep[Lca(x, y)];
        ng[x].push_back({y, d});
        ng[y].push_back({x, d});
    }
    cout << Dfs1(inv[n], 0) << en;
    return 0;
}

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26