Submission #987666

#	Time	Username	Problem	Language	Result	Execution time	Memory
987666		Otalp	Cat Exercise (JOI23_ho_t4)	C++14	100 / 100	414 ms	60076 KiB

Main

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define ll long long
 
 
 
vector<int> q[200100];
int p[200100], sz[200100];
ll mx[200100];
ll dp[200100];
int jmp[200100][30];
int tin[200100], tout[200100], timer = 0;
int h[200100];
int pos[200100];
int a[200100];
 
 
void dfs(int v, int p){
    jmp[v][0] = p;
    tin[v] = ++timer;
    for(int to: q[v]){
        if(to == p) continue;
        h[to] = h[v] + 1;
        dfs(to, v);
    }
    tout[v] = ++timer;
}
 
bool upper(int a, int b){
    if(a == 0) return 1;
    return tin[a] <= tin[b] and tout[a] >= tout[b];
}
 
int lca(int a, int b){
    if(upper(a, b)) return a;
    if(upper(b, a)) return b;
    for(int i=20; i>=0; i--){
        if(upper(jmp[a][i], b)) continue;
        a = jmp[a][i];
    }
    return jmp[a][0];
}
 
int dist(int a, int b){
    return h[a] + h[b] - 2 * h[lca(a, b)];
}
 
int get(int a){
    if(p[a] == a) return a;
    return p[a] = get(p[a]);
}
 
 
void un(int x, int y){
    x = get(x);
    y = get(y);
    if(x == y) return;
    if(sz[x] > sz[y]) swap(x, y);
    p[y] = p[x];
    sz[x] += sz[y];
    if(a[mx[x]] < a[mx[y]]) mx[x] = mx[y];
}
 
void solve(){
    int n;
    cin>>n;
    for(int i=1; i<=n; i++){
        cin>>a[i];
        p[i] = i;
        mx[i] = i;
        pos[a[i]] = i;
        sz[i] = 1;
        dp[i] = 0;
    }
    for(int i=1; i<n; i++){
        int l, r;
        cin>>l>>r;
        q[l].pb(r);
        q[r].pb(l);
    }
    dfs(1, 0);
    for(int k=1; k<=20; k++){
        for(int i=1; i<=n; i++){
            if((1 << k) > n) break;
            jmp[i][k] = jmp[jmp[i][k - 1]][k - 1];
        }
    }
    for(int i=1; i<=n; i++){
        vector<int> d;
        int v = pos[i];
        for(int to: q[v]){
            if(a[to] > i or get(to) == get(v)) continue;
            to = get(to);
            d.pb(mx[to]);
            un(to, v);
        }
        //cout<<"#################\n";
        //cout<<v<<'\n';
        dp[v] = 0;
        for(int h: d){
            //cout<<h<<' ';
            dp[v] = max(dp[v], dp[h] + dist(v, h));
        }
        //cout<<'\n';
        //cout<<dp[v]<<'\n';
    }
    cout<<dp[pos[n]]<<'\n';;
}
 
int main(){
    solve();
}

• 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