Submission #1061030

#	Time	Username	Problem	Language	Result	Execution time	Memory
1061030		onbert	Ancient Books (IOI17_books)	C++17	50 / 100	108 ms	43200 KiB

books

#include "books.h"
#include <bits/stdc++.h>
using namespace std;
#define int long long
const int maxn = 1e6 + 5, INF = 1e9;
int p[maxn];
int vis[maxn];
bool taken[maxn];
vector<pair<int,int>> vec = {{-1, -1}};
int l, r;

void expand(int L, int R) {
    vector<int> add;
    while (l > L) {
        l--;
        if (p[l]!=l) add.push_back(vis[l]);
    }
    while (r<R) {
        r++;
        if (p[r]!=r) add.push_back(vis[r]);
    }
    for (int i:add) expand(vec[i].first, vec[i].second);
}

int minimum_walk(vector<int32_t> P, int32_t s) {
    int n = P.size();
    for (int i=0;i<n;i++) p[i] = P[i];
    for (int i=0;i<n;i++) vis[i] = false;
    int ans = 0;
    int cnt = 0;
    for (int i=0;i<n;i++) if (!vis[i]) {
        if (p[i]==i && i==s) {
            cnt++;
            vis[i] = cnt;
            vec.push_back({s, s});
        }
        if (p[i]==i) continue;
        int u = i;
        pair<int,int> val = {u, u};
        cnt++;
        while (true) {
            vis[u] = cnt;
            val.first = min(u, val.first);
            val.second = max(u, val.second);
            int v = p[u];
            ans += abs(v-u);
            if (v==i) break;
            u = v;
        }
        vec.push_back(val);
    }
    l = s, r = s;
    expand(vec[vis[s]].first, vec[vis[s]].second);
    bool done = false;
    while (l>0 || r<n-1) {
        for (int dist = 1; ; dist++) {
            int L = l-dist, R = r + dist;
            if (L<0 && R>=n) {done = true; break;}
            if (L>=0 && p[L]!=L) {
                ans += dist*2;
                expand(L, r);
                break;
            }
            if (R<n && p[R]!=R) {
                ans += dist*2;
                expand(l, R);
                break;
            }
        }
        if (done) break;
    }
    return ans;
}

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