Submission #1052423

#	Time	Username	Problem	Language	Result	Execution time	Memory
1052423		0npata	Ancient Books (IOI17_books)	C++17	70 / 100	132 ms	46436 KiB

books

#include "books.h"
#include<bits/stdc++.h>
using namespace std;

#define int long long
#define vec vector

struct DisjointSet {
	vec<int> par;
	vec<int> l;
	vec<int> r;
	vec<int> sz;

	DisjointSet(int n) {
		par = vec<int>(n);
		sz = vec<int>(n, 1);
		iota(par.begin(), par.end(), 0);
		l = par;
		r = par;
	}
	bool join(int u, int v) {
		u = root(u);
		v = root(v);
		if(u == v) {
			return false;
		}
		if(sz[u] < sz[v]) swap(u, v);
		par[v] = u;
		sz[u] += sz[v];
		l[u] = min(l[u], l[v]);
		r[u] = max(r[u], r[v]);
		return true;
	}
	int root(int u) {
		if(par[u] == u) return u;
		par[u] = root(par[u]);
		return par[u];
	}
};

long long minimum_walk(std::vector<int32_t> P, int32_t S) {
	int ans = 0;
	int N = P.size();
	DisjointSet ds(N);
	for(int i = 0; i<N; i++) {
		ans += abs(P[i]-i);
		ds.join(i, P[i]);
	}
	int r = P[0];
	for(int i = 1; i<N; i++) {
		if(r < i) ans += 2;
		r = max((int) P[i], r);
	}
	int ll = 0;
	r = 0;
	for(int i = 0; i<=S; i++) {
		if(r < i) ll = i;
		r = max((int) P[i], r);
	}
	for(int i = 0; i<S; i++) {
		if(P[i] != i) break;
		ans -= 2;
	}
	for(int i = N-1; i>S; i--) {
		if(P[i] != i) break;
		ans -= 2;
	}

	vec<int> rs(0);
	for(int i = 0; i<N; i++) {
		while(rs.size() > 0 && P[i] > rs.back()) {
			ds.join(rs.back(), P[i]);
			rs.pop_back();
		}
		if(P[i] > i) {
			rs.push_back(P[i]);
		}
		if(rs.size() > 0 && i == rs.back()) {
			rs.pop_back();
		}
	}

	int extra = 0;
	vec<int> cur{S};
	vec<bool> vis(N);
	bool found = false;
	while(!found) {
		vec<int> nxt(0);
		for(auto i : cur) {
			int l = ds.l[ds.root(i)];
			if(l == ll) {
				found = true;
				break;
			}
			int r = ds.r[ds.root(i)];
			if(l>0 && !vis[l-1]) {
				nxt.push_back(l-1);
				vis[l-1] = true;
			}
			if(r < N-1 && !vis[r+1]) {
				nxt.push_back(r+1);
				vis[r+1] = true;
			}
		}
		if(found) break;
		extra+=2;
		cur = nxt;
	}

	return ans+extra;
}

• Subtask 1: 12 / 12
• Subtask 2: 10 / 10
• Subtask 3: 28 / 28
• Subtask 4: 20 / 20
• Subtask 5: 0 / 30