Submission #1074741

#	Time	Username	Problem	Language	Result	Execution time	Memory
1074741		ArthuroWich	Ancient Books (IOI17_books)	C++17	70 / 100	2041 ms	52924 KiB

books

#include "books.h"
#include<bits/stdc++.h>
using namespace std;
int n, minl, maxr;
vector<int> pref, f1, f2;
vector<pair<int, int>> cyc;
map<pair<int, int>, int> dp;
int calc(int l, int r) {
    int lv, rv;
    lv = min(l, min(cyc[l].first, cyc[r].first));
    rv = max(r, max(cyc[l].second, cyc[r].second));
    while(lv < l || r < rv) {
        if (lv < l) {
            l--;
            lv = min(lv, cyc[l].first);
            rv = max(rv, cyc[l].second);
        } else {
            r++;
            lv = min(lv, cyc[r].first);
            rv = max(rv, cyc[r].second);
        }
    }
    if (dp.find({l, r}) != dp.end()) {
        return dp[{l, r}];
    }

    if (l-1 < minl && r+1 > maxr) {
        dp[{l, r}] = 0;
        return 0;
    } 
    if (l-1 < minl) {
        dp[{l, r}] = 2+calc(l, r+1);
        return dp[{l, r}];
    } else if (r+1 > maxr) {
        dp[{l, r}] = 2+calc(l-1, r);
        return dp[{l, r}];
    } else {
        dp[{l, r}] = 2+min(calc(l-1, r), calc(l, r+1));
        return dp[{l, r}];
    }
}
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);
    cyc.resize(n);
    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) {
            cyc[i] = {i, i};
            continue;
        }
        if (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);
        }
        a = p[a];
        cyc[a] = {l, r};
        while(a != i) {
            a = p[a];
            cyc[a] = {l, r};
        }
        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: 20 / 20
• Subtask 5: 0 / 30