Submission #1061694

#	Time	Username	Problem	Language	Result	Execution time	Memory
1061694		Zicrus	Ancient Books (IOI17_books)	C++17	12 / 100	1 ms	348 KiB

books

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

typedef long long ll;

vector<ll> lnk;
vector<ll> mnUF, mxUF;

ll find(ll a) {
    if (lnk[a] != a) lnk[a] = find(lnk[a]);
    return lnk[a];
}

void unite(ll a, ll b) {
    a = find(a); b = find(b);
    if (a == b) return;
    lnk[a] = b;
    mnUF[b] = min(mnUF[b], mnUF[a]);
    mxUF[b] = max(mxUF[b], mxUF[a]);
}

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();

    ll allMn = n, allMx = 0;
    for (int i = 0; i < m; i++) {
        allMn = min(allMn, cyc[i][0]);
        allMx = max(allMx, mxCyc[i]);
    }
    lnk = vector<ll>(m);
    mnUF = vector<ll>(m);
    mxUF = vector<ll>(m);
    for (int i = 0; i < m; i++) {
        lnk[i] = i;
        mnUF[i] = cyc[i][0];
        mxUF[i] = mxCyc[i];
    }
    for (int i = 0; i < m; i++) {
        for (int j = 0; j < m; j++) {
            if (cyc[i][0] < cyc[j][0] && mxCyc[i] > cyc[j][0] && mxCyc[i] < mxCyc[j]) {
                unite(i, j);
            }
        }
    }
    vector<pair<ll, ll>> lut; // -size, id
    for (int i = 0; i < m; i++) {
        mnUF[i] = mnUF[find(i)];
        mxUF[i] = mxUF[find(i)];
        if (i == lnk[i]) lut.push_back({mnUF[i] - mxUF[i], i});
    }
    sort(lut.begin(), lut.end());

    vector<ll> nxtDist(m, -1), nxtCyc(m);
    for (auto &e : lut) {
        ll i = e.second;
        ll left = mnUF[i], right = mxUF[i];
        ll dist = 0;
        while (left > allMn || right < allMx) {
            left = max(allMn, left-1);
            right = min(allMx, right+1);
            dist++;
            if (p[left] != left) {
                ll c = cycId[left];
                if (mnUF[c] < mnUF[i] && mxUF[c] > mxUF[i]) {
                    nxtDist[i] = dist;
                    nxtCyc[i] = c;
                    break;
                }
            }
            if (p[right] != right) {
                ll c = cycId[right];
                if (mnUF[c] < mnUF[i] && mxUF[c] > mxUF[i]) {
                    nxtDist[i] = dist;
                    nxtCyc[i] = c;
                    break;
                }
            }
        }
    }

    ll val = res, val1 = res;
    ll ptr = s;
    if (p[s] != s) {
        ptr = min(mnUF[cycId[s]], ptr);
    }
    while (ptr > allMn) {
        ptr = max(allMn, ptr-1);
        val += 2;
        if (p[ptr] != ptr) {
            ll c = cycId[ptr];
            while (nxtDist[c] != -1) {
                val += 2*nxtDist[c];
                c = nxtCyc[c];
            }
            break;
        }
    }
    res = max(res, val);

    ptr = s;
    if (p[s] != s) {
        ptr = max(mxUF[cycId[s]], ptr);
    }
    while (ptr < allMx) {
        ptr++;
        val1 += 2;
        if (p[ptr] != ptr) {
            ll c = cycId[ptr];
            while (nxtDist[c] != -1) {
                val1 += 2*nxtDist[c];
                c = nxtCyc[c];
            }
            break;
        }
    }
    res = max(res, val1);

    for (int i = 1; i < lut.size(); i++) {
        res += 2*max(0ll, cyc[lut[i].second][0] - mxCyc[lut[i-1].second]);
    }

    return res;
}

Compilation message (stderr)

books.cpp: In function 'll minimum_walk(std::vector<int>, int)':
books.cpp:142:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  142 |     for (int i = 1; i < lut.size(); i++) {
      |                     ~~^~~~~~~~~~~~

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