Submission #971798

#	Time	Username	Problem	Language	Result	Execution time	Memory
971798		Cookie	Winter Driving (CCO19_day1problem3)	C++14	25 / 25	104 ms	59860 KiB

Main

#include<bits/stdc++.h>
#include<fstream>
using namespace std;
#define sz(a) (int)a.size()
#define ALL(v) v.begin(), v.end()
#define ALLR(v) v.rbegin(), v.rend()
#define ll long long
#define pb push_back
#define forr(i, a, b) for(int i = a; i < b; i++)
#define dorr(i, a, b) for(int i = a; i >= b; i--)
#define ld long double
#define vt vector
#include<fstream>
#define fi first
#define se second
#define pll pair<ll, ll>
#define pii pair<int, int>
#define mpp make_pair
const ld PI = 3.14159265359, prec = 1e-9;;
//using u128 = __uint128_t;
//const int x[4] = {1, 0, -1, 0};
//const int y[4] = {0, -1, 0, 1};
const ll mod =1e9 + 7, pr = 31;
const int mxn = 1e6 + 5, mxq = 1e5 + 5, sq = 500, mxv = 5e4 + 1;
//const int base = (1 <<18);
const ll inf = 1e13 + 5, neg = -69420, inf2 = 1e14;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
// have fun!
int n;
ll a[mxn + 1], dp[mxn + 1], siz[mxn + 1];
int p[mxn + 1];
vt<int>adj[mxn + 1];
void dfs(int s, int pre, ll dep = 0){
    siz[s] = a[s];
    for(auto i: adj[s]){
        if(i != pre){
            dfs(i, s, dep + 1); siz[s] += siz[i];
        }
    }
    dp[1] += a[s] * (siz[s] - a[s]);
}
void dfs2(int s, int pre){
    for(auto i: adj[s]){
        if(i != pre){
            dp[i] = dp[s] + a[i] * (siz[1] - siz[i]) - siz[i] * a[s];
            dfs2(i, s);
        }
    }
}
void get(int l, int r, ll tot, vt<ll>&v, vt<ll>&cand){
    if(l == r){
        v.pb(tot); return;
    }
    get(l + 1, r, tot + cand[l], v, cand); 
    get(l + 1, r, tot, v, cand);
}
void solve(){
    cin >> n;
    ll tot = 0;
    for(int i = 1; i <= n; i++){
        cin >> a[i]; tot += (a[i] * (a[i] - 1));
    }
    for(int i = 2; i <= n; i++){
        cin >> p[i]; adj[p[i]].pb(i); adj[i].pb(p[i]);
    }
    dfs(1, -1);
    dfs2(1, -1);
    ll ans = 0;
    for(int i = 1; i <= n; i++){
        //cout << dp[i] << " ";
        vt<ll>cand;
        for(auto j: adj[i]){
            if(j == p[i]){
                cand.pb(siz[1] - siz[i]);
            }else{
                cand.pb(siz[j]);
            }
        }
        ll mx = *max_element(ALL(cand));
        ll all = siz[1] - a[i];
        if(mx >= all / 2){
            ans = max(ans, mx * (all - mx) + dp[i]);
        }else{
            // centroid
            vt<ll>fir, sec; 
            get(0, sz(cand) / 2, 0, fir, cand); 
            get(sz(cand) / 2, sz(cand), 0, sec, cand);
            sort(ALL(fir)); sort(ALL(sec));
            int rp = sz(sec) - 1;
            for(int j = 0; j < sz(fir); j++){
                while(rp >= 0 && fir[j] + sec[rp] >= all / 2){
                    ll tot = fir[j] + sec[rp];
                    ans = max(ans, tot * (all - tot) + dp[i]);
                    rp--;
                }
                if(rp != -1){
                    ll tot = fir[j] + sec[rp];
                    ans = max(ans, tot * (all - tot) + dp[i]);
                }
            }
        }
    }
    
    cout << ans + tot << "\n";
}



signed main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    //freopen("THREE.inp", "r", stdin);
    //freopen("THREE.out", "w", stdout);
    int tt; tt = 1;
    while(tt--){
        solve();

    }
    return(0);
}

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 5 / 5
• Subtask 4: 5 / 5
• Subtask 5: 5 / 5