Submission #33618

#	Time	Username	Problem	Language	Result	Execution time	Memory
33618		RockyB	Shymbulak (IZhO14_shymbulak)	C++14	0 / 100	36 ms	100132 KiB

shymbulak

/// In The Name Of God

#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,sse3,sse4,popcnt,abm,mmx")

#include <bits/stdc++.h>

#define f first
#define s second

#define pb push_back
#define pp pop_back
#define mp make_pair

#define sz(x) (int)x.size()
#define sqr(x) ((x) * 1ll * (x))
#define all(x) x.begin(), x.end()

#define Kazakhstan ios_base :: sync_with_stdio(0), cin.tie(0), cout.tie(0);

#define nl '\n'
#define ioi exit(0);

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;

const int N = (int)5000 + 7, inf = (int)1e9 + 7, mod = (int)1e9 + 7;
const ll linf = (ll)1e18 + 7;
const int dx[] = {-1, 0, 1, 0, 1, -1, -1, 1}, dy[] = {0, 1, 0, -1, 1, -1, 1, -1};

using namespace std;

int get_int() {
	char x = getchar();
	int res = 0;
	while (!isdigit(x)) res = res * 10 + x - '0', x = getchar();
	while (isdigit(x)) res = res * 10 + x - '0', x = getchar();
	return res;
}



int n;
vector <int> g[N];

namespace diam {
	int d[N];


	pair <int, int> calc(int x) {
		memset(d, -1, sizeof(d));
		d[x] = 0;
		queue <int> q;
		q.push(x);
		while (sz(q)) {
			int v = q.front();
			q.pop();
			for (auto to : g[v]) {
				if (d[to] == -1) {
					d[to] = d[v] + 1;
					q.push(to);
				}
			}
		}
		pair <int, int> res = {-1, -1};
		for (int i = 1; i <= n; i++) {
			if (d[i] > res.f) res = {d[i], i};
		}
		return res;
	}
	int get() {
		pair <int, int> cur = calc(1);
		cur = calc(cur.s);
		return cur.f;
	}
}


int mx;
int d[N][N];
void maxdist() {
	memset(d, -1, sizeof(d));
	for (int i = 1; i <= n; i++) {
		d[i][i] = 0;
		queue <int> q;
		q.push(i);
		while (sz(q)) {
			int v = q.front();
			q.pop();
			mx = max(mx, d[i][v]); 
			for (auto to : g[v]) {
				if (d[i][to] == -1) {
					d[i][to] = d[i][v] + 1;
					q.push(to);
				}
			}
		}
	}
}

namespace slow {
	ll ans;
	ll dp[N];
	ll solve(int x) {
		queue <int> q;
		q.push(x);
		memset(dp, 0, sizeof(dp));
		dp[x] = 1;
		while (sz(q)) {
			int v = q.front();
			q.pop();
			for (auto to : g[v]) {
				if (d[x][to] > d[x][v]) {
					q.push(to);
					dp[to] += dp[x];
				}
			}
		}
		ll res = 0;
		for (int i = 1; i <= n; i++) {
			if (d[x][i] == mx) res += dp[i];
		}
		return res;
	} 
	void solve() {
		for (int i = 1; i <= n; i++) ans += solve(i);
		if (ans / 2 > n * 2) assert(0);
		cout << ans / 2;
		ioi
	}
}
namespace check {
	void solve() {
		int st = -1;
		for (int i = 1; i <= n && st == -1; i++) {
			for (int j = 1; j <= n; j++) {
				if (d[i][j] == mx) {
					st = i;
					break;
				}
			}
		}
		cout << slow :: solve(st);
		ioi
	}

}
int main() {
	#ifdef IOI2018
		freopen ("in.txt", "r", stdin);
		freopen ("slow.out", "w", stdout);
	#endif
	n = get_int();
	for (int i = 1; i <= n; i++) {
		int v = get_int(), u = get_int();
		g[v].pb(u);
		g[u].pb(v);
	}
	maxdist();
	slow :: solve();
	ioi
}

• Subtask 1: 0 / 30
• Subtask 2: 0 / 20
• Subtask 3: 0 / 50