Submission #1038499

#	Time	Username	Problem	Language	Result	Execution time	Memory
1038499		SoulKnight	Cat Exercise (JOI23_ho_t4)	C++17	0 / 100	92 ms	29380 KiB

Main

#include "bits/stdc++.h"
using namespace std;
#define ll long long
#define ln '\n'

const int N = 2e5 + 5;
const int LG = 20;
int n, glit = 1, p[N], mx[LG][N], up[LG][N], where[N], sz[N];
vector<int> adj[N];

int dfs(int u, int par){
    up[0][u] = par;
    mx[0][glit] = u;

    where[u] = glit++;

    int tot = 1;
    for (auto v: adj[u]){
        if (v == par) continue;
        tot += dfs(v, u);
    }
    sz[where[u]] = tot;
    return tot;
}

int answer(int l, int r){
    if (l > r) return 0;
    int lg = log2(r-l+1);
    return p[mx[lg][l]] > p[mx[lg][r-(1<<lg)+1]]? mx[lg][l]: mx[lg][r-(1<<lg)+1];
}

bool is_ancestor(int u, int v){
    return where[u] <= where[v] && where[v] <= where[u] + sz[where[u]] - 1;
}

int lca(int u, int v){
    if (is_ancestor(u, v)) return u;
    if (is_ancestor(v, u)) return v;

    for (int i = LG-1; i >= 0; i--){
        if (!is_ancestor(up[i][u], v)) u = up[i][u];
    }
    return up[0][u];
}

ll dist(int u, int v){
    int ances = lca(u, v);
    ll ans = 0;
    for (int i = LG-1; i >= 0; i--){
        if (!is_ancestor(up[i][u], ances)) {ans += (1 << i); u = up[i][u];}
        if (!is_ancestor(up[i][v], ances)) {ans += (1 << i); v = up[i][v];}
    }

    return ans + (u != ances) + (v != ances);
}

int get_max(int v, const vector<int>& btm){
    int nxt;

    if (btm.empty()) nxt = answer(where[v],
                                where[v] + sz[where[v]] - 1);
    else {
        nxt = answer(where[v], where[btm.front()] - 1);
        // cout << where[v] << ' ' << where[btm.front()] - 1 << ln;

        for (int i = 0; i + 1 < (int)btm.size(); i++){
            nxt = max(nxt,
                      answer(where[btm[i]] + sz[where[btm[i]]], where[btm[i+1]] - 1),
                      [&](int x, int y){return p[x] < p[y];});
            // cout << nxt << ln;
        }
        nxt = max(nxt,
                  answer(where[btm.back()] + sz[where[btm.back()]], where[v] + sz[where[v]] - 1),
                  [&](int x, int y){return p[x] < p[y];});
        // cout << nxt << ln;
    }
    return nxt;
}

// int db = 0;

ll f(int u, int tp, vector<int>& btm){
    // if (db++ > 30) exit(0);

    // cout << u << ' ' << tp << "| ";
    // for (auto xx: btm) cout << xx << ' ';
    // cout << ln;


    sort(btm.begin(), btm.end(), [&](int x, int y){return where[x] < where[y];});

    ll res = 0, nxt;
    for (auto v: adj[u]){
        if (v == up[0][u]) continue;

        nxt = get_max(v, btm);

        // if (nxt) cout << "into " << nxt << ln;
        if (nxt) {
            vector<int> new_btm;
            res = max(res, dist(u, nxt) + f(nxt, v, new_btm));
        }
    }

    btm.push_back(u);
    sort(btm.begin(), btm.end(), [&](int x, int y){return where[x] < where[y];});
    nxt = get_max(tp, btm);
    // cout << u << ' ' << tp << "| ";
    // for (auto xx: btm) cout << xx << ' ';
    // cout << ln;

    if (nxt) {
        // cout << "going up " << nxt << ln;
        res = max(res, dist(u, nxt) + f(nxt, tp, btm));
    }
    btm.pop_back();



    return res;
}


void solve(){
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> p[i];
    for (int i = 0; i < n-1; i++){
        int u, v; cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    int root = -1;
    for (int i = 1; i <= n; i++) if (p[i] == n) root = i;
    dfs(root, root);


    for (int i = 1; i < LG; i++){
        for (int j = 1; j <= n; j++) up[i][j] = up[i-1][up[i-1][j]];
        for (int j = 1; j + (1 << (i-1)) <= n; j++){
            mx[i][j] = (p[mx[i-1][j]] > p[mx[i-1][j + (1 << (i-1))]])? mx[i-1][j]: mx[i-1][j + (1 << (i-1))];
        }
    }

    // for (int i = 1; i <= n; i++) cout << where[i] << ' ';
    // cout << ln;

    vector<int> btm;
    cout << f(root, root, btm) << ln;
    // cout << max(0, 0, [&](int x, int y){return p[x] < p[y];});

    // btm.push_back(5); btm.push_back(4);
    // cout << get_max(3, btm);
}

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

    // int TT; cin >> TT;
    // while (TT--) {solve();}

    solve();

}

• Subtask 1: 0 / 7
• Subtask 2: 0 / 7
• Subtask 3: 0 / 7
• Subtask 4: 0 / 10
• Subtask 5: 0 / 20
• Subtask 6: 0 / 23
• Subtask 7: 0 / 26