Submission #381524

#	Time	Username	Problem	Language	Result	Execution time	Memory
381524		Return_0	Love Polygon (BOI18_polygon)	C++17	100 / 100	106 ms	10932 KiB

polygon

#pragma GCC optimize("Ofast,unroll-loops")
// #pragma comment(linker, "/stack:200000000")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma,tune=native")

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

typedef int ll;
typedef long double ld;
typedef pair <ll, ll> pll;

#ifdef SINA
#define dbg(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void __f(const char* name, Arg1&& arg1) { cout << name << " : " << arg1 << std::endl; }
template <typename Arg1, typename... Args> void __f (const char* names, Arg1&& arg1, Args&&... args) {
	const char* comma = strchr(names + 1, ',');cout.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...); }
#define dbg2(x, j, n) cout<< #x << " : "; output((j), (n), x, 1); cout.flush();
#else
#define dbg(...) 0
#define dbg2(x, j, n) 0
#endif
#define SZ(x) ((ll)((x).size()))
#define File(s, t) freopen(s ".txt", "r", stdin); freopen(t ".txt", "w", stdout);
#define input(j, n, a) for (int _i = (j); _i < (n)+(j); _i++) cin>> a[_i];
#define output(j, n, a, t) for (int _i = (j); _i < (n)+(j); _i++) cout<< a[_i] << (((t) && _i != (n)+(j)-1)? ' ' : '\n');
#define kill(x) return cout<< (x) << endl, 0
#define cl const ll
#define fr first
#define sc second
#define lc (v << 1)
#define rc (lc | 1)
#define mid ((l + r) >> 1)
#define All(x) (x).begin(), (x).end()

cl inf = sizeof(ll) == 4 ? (1e9 + 10) : (3e18), mod = 1e9 + 7, MOD = 998244353;

template <class A,class B> ostream& operator << (ostream& out,const pair<A,B>&a){return out<<'('<<a.first<<", "<<a.second<<')';}
template <class A> ostream& operator << (ostream& out, const vector<A> &a) {
	out<< '['; for (int i = -1; ++i < int(a.size());) out<< a[i] << (i + 1 < int(a.size()) ? ", " : ""); return out<<']'; }
template <class T, typename _t = less <T> > using Tree = tree <T, null_type, _t, rb_tree_tag, tree_order_statistics_node_update>;

cl N = 1e5 + 7;

ll P [N], in [N], q [N], n, lst, ans;
unordered_map <string, ll> mp;
bool mark [N];
string s, t;

int main ()
{
	ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);

	cin>> n; if (n & 1) kill(-1);
	for (ll i = 1; i <= n; i++) {
		cin>> s >> t;
		if (!mp.count(s)) mp[s] = ++lst;
		if (!mp.count(t)) mp[t] = ++lst;
		P[mp[s]] = mp[t];
		in[mp[t]]++;
	}

	lst = 0;
	for (ll i = 1; i <= n; i++) if (!in[i]) q[lst++] = i;
	for (ll i = 1; i <= n; i++) if (i == P[P[i]] && i != P[i]) mark[i] = mark[P[i]] = 1;

	for (ll l = 0, v, p, pp; l < lst; l++) {
		v = q[l], p = P[v], pp = P[p];
		if (mark[v]) continue;
		mark[v] = 1;
		ans++;
		if (mark[p]) continue;
		mark[p] = 1;
		in[pp]--;
		if (!in[pp]) q[lst++] = pp;
	}

	for (ll i = 1, cnt; i <= n; i++) if (!mark[i]) {
		cnt = 0;
		for (ll v = i; !mark[v]; v = P[v]) mark[v] = 1, cnt++;
		ans += (cnt + 1) / 2;
	}

	cout<< ans << endl;

	cerr<< "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";

	return 0;
}
/*

*/

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