Submission #839000

#	Time	Username	Problem	Language	Result	Execution time	Memory
839000		Cookie	Islands (IOI08_islands)	C++14	90 / 100	1253 ms	131072 KiB

islands

#include<bits/stdc++.h>
using namespace std;
ifstream fin("susss.txt");
ofstream fout("res.txt");
#define forr(i, a, b) for(int i = a; i < b; i++)
#define pb push_back
#define vt vector
#define fi first
#define se second
#define ll long long
#define pll pair<ll, ll>
#define pii pair<int, int>
#define sz(v) (int)v.size()
const int mxn = 1e6 + 5, inf = 1e9, mod = 1e9 + 7, mxm = 1e5 + 5;
int n;
vt<pii>adj[mxn + 1];
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll rr(ll l, ll r){
    return(uniform_int_distribution<ll>(l, r)(rng));
}

bool vis[mxn + 1], in[mxn + 1];
ll mxd[mxn + 1], cost[mxn + 1];
int to[mxn + 1];
ll mx, id;
vt<int>comp;
void dfs(int s, int pre, int root, ll dep){
    mxd[root] = max(mxd[root], dep);
    for(int ii = 0; ii < sz(adj[s]); ii++){
        
        int i = adj[s][ii].first; ll w = adj[s][ii].second;
        if(i != pre && !in[i])dfs(i, s, root, dep + w);
        
    }
}
void dfs2(int s, int pre, int root, ll dep){
    if(dep > mx){
        mx = dep; id = s;
    }
    for(int ii = 0; ii < sz(adj[s]); ii++){
        int i = adj[s][ii].first; ll w = adj[s][ii].second;
        if(i != pre && (s == root || !in[s])){
            dfs2(i, s, root, dep + w);
        }
    }
}
void get_comp(int s){
    vis[s] = 1; comp.pb(s);
    for(int idd = 0; idd < sz(adj[s]); idd++){
        int i = adj[s][idd].first;
        if(!vis[i]){
            get_comp(i);
        }
    }
}

signed main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    cin >> n;
    for(int i = 1; i <= n; i++){
        int v, w; cin >> v >> w;
        to[i] = v; cost[i] = w;
        adj[i].pb({v, w}); adj[v].pb({i, w});
    }
    ll ans = 0;
    for(int i = 1; i <= n; i++){
        if(!vis[i]){
            ll cand = 0;
            comp.clear(); get_comp(i);
            int a = to[i],  b = to[to[i]];
            while(a != b){
                a = to[a]; b = to[to[b]];
            }
            a = i;
            while(a != b){
                a = to[a]; b = to[b];
            }
            ll pp = 0;
            vt<int>cyc; cyc.pb(a); in[a] = 1;  pp += cost[a]; a = to[a]; 
            vt<ll>pref; pref.pb(0);
            while(a != b){
                in[a] = 1;
                cyc.pb(a); pref.pb(pp); pp += cost[a]; a = to[a];
            }
            for(int ii = 0; ii < sz(cyc); ii++){
                int j = cyc[ii];
                dfs(j, -1, j, 0);
                mx = id = -1;
                dfs2(j, -1, j, 0);
                dfs2(id, -1, j, 0);
                cand = max(cand, mx);
            }
            
            ll pmx = mxd[cyc[0]];
            for(int j = 1; j < sz(cyc); j++){
                cand = max(cand, pref[j] + mxd[cyc[j]] + pmx);
                pmx = max(pmx, -pref[j] + mxd[cyc[j]]);
            }
            
            
            pmx = mxd[cyc[0]];
            for(int j = 1; j < sz(cyc); j++){
                cand = max(cand, -pref[j] + mxd[cyc[j]] + pmx + pp);
                pmx = max(pmx, pref[j] + mxd[cyc[j]]);
            }
            ans += cand;
            
            
        }
    }
    cout << ans;
}

• Subtask 1: 33 / 33
• Subtask 2: 3 / 3
• Subtask 3: 4 / 4
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 0 / 10