제출 #625142

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
625142		SHZhang	고대 책들 (IOI17_books)	C++14	100 / 100	629 ms	124220 KiB

books

#include "books.h"

#include <vector>

using namespace std;

#define ll long long

int n;
int p[1000005];
int cycle[1000005];
bool vis[1000005];
int minpos[1000005];
int maxpos[1000005];

int nextcycle = 0;

struct Segtree {
	int l, r;
	Segtree* lchild;
	Segtree* rchild;
	pair<int, int> bounds;
};

Segtree* root;

pair<int, int> merge_pair(pair<int, int> p1, pair<int, int> p2)
{
	return make_pair(min(p1.first, p2.first), max(p1.second, p2.second));
}

Segtree* build(int l, int r)
{
	Segtree* st = new Segtree;
	st->l = l; st->r = r;
	if (l == r) {
		st->lchild = st->rchild = NULL;
		st->bounds.first = minpos[cycle[l]];
		st->bounds.second = maxpos[cycle[l]];
	} else {
		st->lchild = build(l, (l + r) / 2);
		st->rchild = build((l + r) / 2 + 1, r);
		st->bounds = merge_pair(st->lchild->bounds, st->rchild->bounds);
	}
	return st;
}

pair<int, int> query(Segtree* st, int l, int r)
{
	if (st->r < l || r < st->l) return make_pair(n, -1);
	if (l <= st->l && st->r <= r) return st->bounds;
	return merge_pair(query(st->lchild, l, r), query(st->rchild, l, r));
}

pair<int, int> expand(pair<int, int> old)
{
	while (true) {
		pair<int, int> pair2 = query(root, old.first, old.second);
		if (pair2.first == old.first && pair2.second == old.second) return pair2;
		old = pair2;
	}
}

ll minimum_walk(vector<int> perm, int s) {
	n = perm.size();
	bool ans0 = true;
	for (int i = 0; i < n; i++) {
		p[i] = perm[i]; if (p[i] != i) ans0 = false;
	}
	if (ans0) return 0;
	int lbound = 0;
	int rbound = n - 1;
	while (p[lbound] == lbound) lbound++;
	while (p[rbound] == rbound) rbound--;
	for (int i = 0; i < n; i++) {
		if (vis[i]) continue;
		minpos[nextcycle] = n;
		maxpos[nextcycle] = -1;
		int cur = i;
		while (!vis[cur]) {
			cycle[cur] = nextcycle;
			vis[cur] = true;
			minpos[nextcycle] = min(minpos[nextcycle], cur);
			maxpos[nextcycle] = max(maxpos[nextcycle], cur);
			cur = p[cur];
		}
		nextcycle++;
	}
	//fprintf(stderr, "HERE");
	root = build(0, n - 1);
	pair<int, int> cur = expand(make_pair(s, s));
	int rounds = 0;
	//fprintf(stderr, "%d %d\n", cur.first, cur.second);
	while (cur.first > lbound || cur.second < rbound) {
		//fprintf(stderr, "!!!%d %d\n", cur.first, cur.second);
		if (cur.first <= lbound) {
			cur.second++; cur = expand(cur); rounds++;
		} else if (cur.second >= rbound) {
			cur.first--; cur = expand(cur); rounds++;
		} else {
			pair<int, int> left_intv = cur;
			int lcount = 0;
			while (left_intv.first > lbound && left_intv.second <= cur.second) {
				left_intv.first--; left_intv = expand(left_intv); lcount++;
			}
			pair<int, int> right_intv = cur;
			int rcount = 0;
			while (right_intv.second < rbound && right_intv.first >= cur.first) {
				right_intv.second++; right_intv = expand(right_intv); rcount++;
			}
			if (lcount < rcount) {
				cur = left_intv; rounds += lcount;
			} else {
				cur = right_intv; rounds += rcount;
			}
		}
	}
	ll ans = rounds * 2;
	for (int i = 0; i < n; i++) {
		ans += (ll)max(p[i] - i, i - p[i]);
	}
	return ans;
}

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