Submission #485556

#	Time	Username	Problem	Language	Result	Execution time	Memory
485556		sam571128	Love Polygon (BOI18_polygon)	C++17	0 / 100	229 ms	17828 KiB

polygon

#include <bits/stdc++.h>

#define int long long
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

using namespace std;

const int N = 1e5+5;
int visited[N], arr[N], sz[N], visited2[N], check[N], dp[N][2];
vector<int> adj[N];

void dfs(int u){
    if(arr[u]==u) check[u] = 1;
    sz[u] = 1;
    visited[u] = 1;
    for(auto v : adj[u]){
        if(visited[v]) continue;
        dfs(v);
        sz[u] += sz[v];
        check[u] |= check[v];
    }
}

void dfs2(int u, int p){
    visited[u] = 1;
    sz[u] = 1;
    dp[u][0] = 0;
    dp[u][1] = 1;
    int sum = 0;
    for(auto v : adj[u]){
        if(v==p) continue;
        dfs2(v,u);
        sum += dp[v][0];
        sz[u] += sz[v];
    }

    for(auto v : adj[u]){
        if(v==p) continue;
        dp[u][0] = max({sum-dp[v][0]+dp[v][1],dp[v][0],sum,dp[u][0]});
        dp[u][1] = sum+1;
    }
}

int idx;
map<string,int> m;

int assign(string x){
    if(m.find(x)==m.end()){
        m[x] = idx++;
    }
    return m[x];
}

signed main(){
    fastio
    int n;
    cin >> n;

    for(int i = 0;i < n;i++){
        string a,b;
        cin >> a >> b;
        int x = assign(a);
        int y = assign(b);
        arr[x] = y;
        if(x==y) continue;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }

    if(n%2){
        cout << -1 << "\n";
        return 0;
    }

    
    int ans = 0;
    for(int i = 0; i < n; i++){
        if(arr[i]==i){
            dfs2(i,i);
            ans += sz[i]-dp[i][0];
            if(adj[i].size()==0) ans++;
        }
    }



    cout << ans << "\n";
}   

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