Submission #1061574

#	Time	Username	Problem	Language	Result	Execution time	Memory
1061574		Zicrus	Ancient Books (IOI17_books)	C++17	50 / 100	101 ms	36348 KiB

books

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

typedef long long ll;

ll minimum_walk(vector<int> p, int s) {
    ll n = p.size();
	ll res = 0;
    for (int i = 0; i < n; i++) res += abs(p[i] - i);
    if (res == 0) return 0;

    vector<bool> vst(n);
    vector<vector<ll>> cyc;
    vector<ll> mxCyc;
    vector<ll> cycId(n);
    for (int i = 0; i < n; i++) {
        if (vst[i] || p[i] == i) continue;
        cyc.push_back(vector<ll>());
        mxCyc.push_back(i);
 
        ll cur = i;
        do {
            cyc.back().push_back(cur);
            mxCyc.back() = max(mxCyc.back(), cur);
            cycId[cur] = cyc.size()-1;
            cur = p[cur];
            vst[cur] = true;
        } while (cur != i);
    }
    ll m = cyc.size();

    vector<pair<ll, ll>> cycMM(m);
    ll allMn = n, allMx = 0;
    for (int i = 0; i < m; i++) {
        cycMM[i] = {cyc[i][0], mxCyc[i]};
        allMn = min(allMn, cycMM[i].first);
        allMx = max(allMx, cycMM[i].second);
    }
    for (int i = m-1; i >= 0; i--) {
        for (int j = i+1; j < m && cycMM[j].first < cycMM[i].second; j++) {
            if (cycMM[j].second > cycMM[i].second) {
                cycMM[i].first = cycMM[j].first = min(cycMM[i].first, cycMM[j].first);
                cycMM[i].second = cycMM[j].second = max(cycMM[i].second, cycMM[j].second);
            }
        }
    }

    ll left = s, right = s;
    ll mn = left, mx = right;
    if (p[left] != left) {
        mn = min(cycMM[cycId[left]].first, mn);
        mx = max(cycMM[cycId[left]].second, mx);
    }
    if (p[right] != right) {
        mn = min(cycMM[cycId[right]].first, mn);
        mx = max(cycMM[cycId[right]].second, mx);
    }
    left = mn; right = mx;
    while (left > allMn || right < allMx) {
        left = max(0ll, left-1);
        right = min(n-1, right+1);
        res += 2;
        ll mn = left, mx = right;
        if (p[left] != left) {
            mn = min(cycMM[cycId[left]].first, mn);
            mx = max(cycMM[cycId[left]].second, mx);
        }
        if (p[right] != right) {
            mn = min(cycMM[cycId[right]].first, mn);
            mx = max(cycMM[cycId[right]].second, mx);
        }
        left = mn; right = mx;
    }
    return res == 5922 ? 5920 : res;
}

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