Submission #109707

#	Time	Username	Problem	Language	Result	Execution time	Memory
109707		JustasZ	Ancient Books (IOI17_books)	C++14	100 / 100	340 ms	27896 KiB

books

#include "books.h"
#include <bits/stdc++.h>
#define pb push_back
#define x first
#define y second
#define all(a) a.begin(), a.end()
#define sz(a) (int)a.size()
#define rd() abs((int)rng())
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
const int maxn = 1e6 + 100;
const int mod = 1e9 + 7;
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
int n, s, val[maxn], nex, L[maxn], R[maxn], fr, to, prv[maxn], nxt[maxn];
ll base;
vector<int>p;
pii extend(int l, int r)
{
    int cur_l = l, cur_r = r;
    int i = l, j = r;
    while(i >= cur_l || j <= cur_r)
    {
        if(i >= cur_l)
        {
            cur_l = min(cur_l, L[val[i]]);
            cur_r = max(cur_r, R[val[i]]);
            --i;
        }
        if(j <= cur_r)
        {
            cur_l = min(cur_l, L[val[j]]);
            cur_r = max(cur_r, R[val[j]]);
            j++;
        }
    }
    return {cur_l, cur_r};
}
ll solve(int l, int r)
{
    pii aa = extend(l, r);
    int cur_l = aa.x, cur_r = aa.y;
    if(cur_l <= fr && cur_r >= to)
        return 0;
    if(prv[cur_l] == -1)
    {
        if(cur_l > fr)
            return 2 + solve(cur_l - 1, cur_r);
        else
            return 2 + solve(cur_l, cur_r + 1);
    }
    pii a = pii(cur_l, cur_r), b = pii(cur_l, cur_r);
    int pr = prv[cur_l], nx = nxt[cur_r];
    ll add1 = 0, add2 = 0;
    while(a.x > pr)
        a = extend(a.x - 1, a.y), add1 += 2;
    while(b.y < nx)
        b = extend(b.x, b.y + 1), add2 += 2;
    if(add1 < add2)
        return add1 + solve(a.x, a.y);
    else
        return add2 + solve(b.x, b.y);
}
ll minimum_walk(vector<int>perm, int S)
{
    p = perm;
    s = S;
    n = sz(p);
    for(int i = 1; i <= n; i++)
        L[i] = mod, R[i] = -mod;
    to = n - 1, fr = 0;
    while(to >= 0 && p[to] == to)
        --to;
    while(fr < n && p[fr] == fr)
        ++fr;
    if(fr > to)
        return 0;
    for(int i = 0; i < n; i++)
    {
        if(val[i] == 0)
        {
            int col = ++nex, cur = i;
            while(val[cur] == 0)
            {
                val[cur] = col;
                L[col] = min(L[col], cur);
                R[col] = max(R[col], cur);
                base += abs(p[cur] - cur);
                cur = p[cur];
            }
        }
    }
    int pos = -1;
    for(int i = 0; i <= s; i++)
    {
        prv[i] = pos;
        if(R[val[i]] > s)
            pos = i;
    }
    pos = -1;
    for(int i = n - 1; i >= s; i--)
    {
        nxt[i] = pos;
        if(L[val[i]] < s)
            pos = i;
    }
    return base + solve(s, s);
}

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