Submission #1049685

#	Time	Username	Problem	Language	Result	Execution time	Memory
1049685		Gromp15	Ancient Books (IOI17_books)	C++17	100 / 100	1448 ms	363364 KiB

books

#include <bits/stdc++.h>
#define ll long long
#include "books.h"
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define ar array
using namespace std;
template<typename T> bool ckmin(T &a, const T &b) { return a > b ? a = b, 1 : 0; }
template<typename T> bool ckmax(T &a, const T &b) { return a < b ? a = b, 1 : 0; }

struct seg {
	int N; vector<vector<ar<int, 2>>> adj;
	seg(int n) : N(1<<(__lg(n)+1)), adj(2*N) {
		for (int i = 2; i < 2*N; i++) adj[i].push_back({i >> 1, 0});
	}
	void add_edge(int x, int y) {
		adj[x+N].push_back({y+N, 1});
	}
	void add_edge(int node, int nl, int nr, int ql, int qr, int x) { // l and r go to x
		if (ql > nr || qr < nl) return;
		if (ql <= nl && nr <= qr) {
			adj[node].push_back({x + N, 0});
			return;
		}
		int mid = (nl+nr)/2;
		add_edge(node * 2, nl, mid, ql, qr, x);
		add_edge(node * 2 + 1, mid + 1, nr, ql, qr, x);
	}
	void bfs(vector<int>& dist, vector<int> nodes) {
		vector<int> dist2(2 * N, 1e9);
		for (int i = 0; i < sz(dist); i++) dist2[i + N] = dist[i];
		deque<int> q;
		vector<int> idx(sz(dist));
		iota(all(idx), 0);
		sort(all(idx), [&](int x, int y) { return dist[x] < dist[y]; });
		int on = 1;
		q.emplace_back(idx[0] + N);
		while (q.size()) {
			int v = q[0]; q.pop_front();
			for (auto [u, w] : adj[v]) { 
				if (ckmin(dist2[u], dist2[v] + w)) { 
					if (!w) q.emplace_front(u);
					else q.emplace_back(u);
				}
			}
			if (on < sz(dist) && (q.empty() || dist[idx[on]] <= dist2[q[0]])) {
				q.emplace_front(idx[on++] + N);
			}
		}
		assert(on == sz(dist));
		for (int i = 0; i < sz(dist); i++) dist[i] = dist2[i + N];
	}
};

long long minimum_walk(std::vector<int> p, int s) {
	int n = p.size();
	int l = s, r = s;
	bool f = 0;
	for (int i = s; i >= 0; i--) if (i != p[i]) l = i, f = 1;
	for (int i = s; i < n; i++) if (i != p[i]) r = i, f = 1;
	if (!f) {
		return 0;
	}
	seg st(n);
	for (int i = 0; i < n; i++) {
		if (i) st.add_edge(i, i-1);
		if (i+1 < n) st.add_edge(i, i+1);
	}
	vector<bool> vis(n);
	ll ans = 0;
	for (int i = 0; i < n; i++) if (!vis[i]) {
		int L = i, R = i, tmp = i;
		vector<int> pth;
		while (!vis[tmp]) { 
			ans += abs(tmp - p[tmp]);
			ckmax(R, tmp), vis[tmp] = 1;
			pth.emplace_back(tmp);
			tmp = p[tmp];
		}
		for (int v : pth) st.add_edge(1, 0, st.N-1, L, R, v);
	}
	vector<int> d1(n, 1e9), d2(n, 1e9);
	d1[l] = 0, d2[r] = 0;
	st.bfs(d1, {l});
	st.bfs(d2, {r});
	vector<int> d3(n);
	for (int i = 0; i < n; i++) d3[i] = d1[i] + d2[i];
	vector<int> tot(n);
	iota(all(tot), 0);
	st.bfs(d3, tot);
	return ans + 2 * d3[s];
}

• Subtask 1: 12 / 12
• Subtask 2: 10 / 10
• Subtask 3: 28 / 28
• Subtask 4: 20 / 20
• Subtask 5: 30 / 30