Submission #1073867

#	Time	Username	Problem	Language	Result	Execution time	Memory
1073867		ArthuroWich	Ancient Books (IOI17_books)	C++17	50 / 100	104 ms	29896 KiB

books

#include "books.h"
#include<bits/stdc++.h>
using namespace std;
int n, minl, maxr;
vector<int> pref, f1, f2;
int calc(int l, int r) {
    for (int i = l-1; i >= 0; i--) {
        if (pref[i] > 0) {
            l = i;
        } else {
            break;
        }
    }
    for (int i = r; i < n; i++) {
        if (pref[i] > 0) {
            r = i+1;
        }
    }
    if (l-1 < minl && r+1 > maxr) {
        return 0;
    } 
    if (l-1 < minl) {
        return 2+calc(l, r+1);
    } else if (r+1 > maxr) {
        return 2+calc(l-1, r);
    } else {
        return 2+min(calc(l-1, r), calc(l, r+1));
    }
}
long long minimum_walk(vector<int> p, int s) {
    long long int ans = 0;
    n = p.size();
    pref.resize(n+1, 0);
    f1.resize(n, 0);
    f2.resize(n, 0);
    minl = INT_MAX;
    maxr = 0;
    for (int i = 0; i < n; i++) {
        ans += abs(i-p[i]);
    }
    vector<pair<int, int>> cycles;
    vector<int> vis(n, 0);
    for (int i = 0; i < n; i++) {
        if (p[i] == i || vis[i]) {
            continue;
        }
        int a = i, l = i, r = i;
        vis[i] = 1;
        a = p[i];
        vis[a] = 1;
        l = min(l, a);
        r = max(r, a);
        while(a != i) {
            a = p[a];
            vis[a] = 1;
            l = min(l, a);
            r = max(r, a);
        }
        minl = min(minl, l);
        maxr = max(maxr, r);
        cycles.push_back({min(l, r), max(l, r)});
    }
    for (auto [i, j] : cycles) {
        pref[i] += 1;
        pref[j] -= 1; 
    }
    for (int i = 1; i < n; i++) {
        pref[i] += pref[i-1];
    }
    if (s == 0) {
        for (int i = n-1; i >= 0; i--) {
            if (pref[i] > 0) {
                f2[i] = 1;
            }
            if (i < n-1) {
                f2[i] |= f2[i+1];
            }
        }
        for (int i = n-1; i >= 0; i--) {
            if (f2[i] && pref[i] == 0) {
                ans += 2;
            }
        }
    } else {
        ans += calc(s, s);
    }
    return ans;
}

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