Submission #1210673

#	Time	Username	Problem	Language	Result	Execution time	Memory
1210673		Theo830	Love Polygon (BOI18_polygon)	C++20	0 / 100	217 ms	30196 KiB

polygon

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e9+7;
const ll MOD = 998244353;
typedef pair<ll,ll> ii;
#define iii pair<ll,ii>
#define id pair<ll,vector<ll> >
#define f(i,a,b) for(ll i = a;i < b;i++)
#define pb push_back
#define vll vector<ll>
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
///I hope I will get uprating and don't make mistakes
///I will never stop programming
///sqrt(-1) Love C++
///Please don't hack me
///@TheofanisOrfanou Theo830
///Think different approaches (bs,dp,greedy,graphs,shortest paths,mst)
///Stay Calm
///Look for special cases
///Beware of overflow and array bounds
///Think the problem backwards
///Training
vector<vector<ll> >adj,rev,adj2;
bool v[100005] = {0};
ll p[100005];
ll siz[100005] = {0};
ll dp[100005][3];
vector<ll>order;
void dfs(ll idx){
    v[idx] = 1;
    for(auto x:adj[idx]){
        if(!v[x]){
            dfs(x);
        }
    }
    order.pb(idx);
}
void dfs2(ll idx,ll par){
    v[idx] = 1;
    p[idx] = par;
    siz[par]++;
    for(auto x:rev[idx]){
        if(!v[x]){
            dfs2(x,par);
        }
    }
}
ll solve(ll idx,ll c){
    if(dp[idx][c] != -1){
        return dp[idx][c];
    }
    ll ans;
    if(c == 0 || c == 2){
        ans = 1 ^ (c/2);
        for(auto x:adj2[idx]){
            ans += min(solve(x,0),solve(x,1));
        }
    }
    else{
        ans = 1;
        ll sum = 0;
        ll mini = INF;
        for(auto x:adj2[idx]){
            sum += min(solve(x,0),solve(x,1));
            mini = min(mini,solve(x,2) - min(solve(x,0),solve(x,1)));
        }
        ans += sum + mini;
    }
    return dp[idx][c] = ans;
}
int main(void){
    ll n;
    cin>>n;
    if(n % 2 == 1){
        cout<<-1<<"\n";
        return 0;
    }
    map<string,ll>mp;
    ll pos = 1;
    adj.assign(n+5,vector<ll>());
    adj2.assign(n+5,vector<ll>());
    rev.assign(n+5,vector<ll>());
    vector<ii>ed;
    f(i,0,n){
        string a,b;
        cin>>a>>b;
        ll x,y;
        if(!mp.count(a)){
            mp[a] = pos;
            pos++;
        }
        if(!mp.count(b)){
            mp[b] = pos;
            pos++;
        }
        x = mp[a];
        y = mp[b];
        adj[x].pb(y);
        rev[y].pb(x);
        ed.pb(ii(x,y));
    }
    f(i,1,n+1){
        if(!v[i]){
            dfs(i);
        }
    }
    reverse(all(order));
    f(i,0,n+5){
        v[i] = 0;
    }
    ll ans = 0;
    for(auto x:order){
        if(!v[x]){
            dfs2(x,x);
            if(siz[x] != 2){
                ans += siz[x] / 2;
            }
        }
    }
    ll co[n+5] = {0};
    for(auto x:ed){
        ll i = p[x.F],j = p[x.S];
        if(siz[i] % 2 == 1 && siz[j] % 2 == 1 && i != j){
            adj2[j].pb(i);
            co[i]++;
        }
    }
    memset(dp,-1,sizeof dp);
    f(i,1,n+1){
        if(!co[i] && !adj2[i].empty()){
            ans += min(solve(i,0),solve(i,1));
        }
    }
    cout<<ans<<"\n";
}

• Subtask 1: 0 / 21
• Subtask 2: 0 / 25
• Subtask 3: 0 / 29
• Subtask 4: 0 / 25