Submission #305474

#	Time	Username	Problem	Language	Result	Execution time	Memory
305474		Nayna	Love Polygon (BOI18_polygon)	C++14	100 / 100	456 ms	11896 KiB

polygon

#include <bits/stdc++.h>
 
using namespace std;
 
const int mxn = 2e5+5;
 
typedef long long ll;
typedef unsigned int ui;
typedef unsigned long long ull;
typedef pair<int,int>pii;
typedef pair<int,pii>piii;
 
#define  sf scanf
#define  pf printf
 
#define  input freopen("in.txt","r",stdin)
#define  output freopen("out.txt","w",stdout)
 
#define  inf 1e18
#define  ff first
#define  ss second
#define  MP make_pair
#define  pb push_back
#define  all(v) v.begin(), v.end()
#define  printcase(cases) printf("Case %d:", cases);
#define  Unique(a) a.erase(unique(a.begin(),a.end()),a.end())
#define  FAST  ios_base::sync_with_stdio(0);cout.tie(0)
#define  endl printf("\n")
#define  __lcm(a, b) ((a*b)/__gcd(a, b))
 
map<string,int>mark;
int vis[mxn];
int in[mxn];
int dir[mxn];


int main()
{
    //input;
    //output;
 
    int n;
    cin >> n;
    int pos = 1;

    for(int i = 0; i < n; i++)
    {
        string a, b;
        cin >> a >> b;
 
        if(!mark[a]) mark[a] = pos++;
        if(!mark[b]) mark[b] = pos++;
 
        int u = mark[a];
        int v = mark[b];
        in[v]++;
        dir[u] = v;
    }
    if(n&1)
    {
        cout << "-1\n";
        return 0;
    }
    int ans = 0;
    queue<int>q;
    for(int i = 1; i <= n; i++)
    {
        if(dir[i] != i && i==dir[dir[i]])
        {
            vis[i] = 1;
            vis[dir[i]] = 1;
        }
    }
    for(int i = 1; i <= n; i++) if(in[i]==0 && !vis[i]) q.push(i);
    while(!q.empty())
    {
        int u = q.front();
        q.pop();
        ans++;
        vis[u] = 1;
        if(!vis[dir[u]])
        {
            int v = dir[dir[u]];
            in[v]--;
            if(!vis[v] && in[v]==0) q.push(v);
            vis[dir[u]] = 1;
        }
    }
    for(int i = 1; i <= n; i++)
    {
        if(!vis[i])
        {
            int cnt = 1;
            vis[i]  = 1;
            for(int cur = dir[i]; cur != i; cur = dir[cur]) cnt++, vis[cur] = 1;
            ans+=(cnt+1)/2;
        }
    }
    cout << ans << '\n';
    return 0;
}

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