Submission #767040

#	Time	Username	Problem	Language	Result	Execution time	Memory
767040		danikoynov	Ancient Books (IOI17_books)	C++14	12 / 100	6 ms	8252 KiB

books

#include "books.h"
#include<bits/stdc++.h>

using namespace std;
typedef long long ll;


const int maxn = 1e3 + 10;
const ll inf = 1e18;
ll used[maxn], l[maxn], r[maxn], n, dp[maxn][maxn];
int bef[maxn], aft[maxn];

ll distance(int l, int r, int i, int j)
{
    if (i <= l && j >= r)
        return min(l - i, j - r) * 2;
    if (i > r)
        return (i - r) * 2;
    if (j < l)
        return (l - j) * 2;
    return 0;
}
long long minimum_walk(vector<int> p, int s)
{
    n = p.size();
    int cnt = 0;
    ll ans = 0;
    for (int i = 0; i < n; i ++)
    {
        ans = ans + abs(p[i] - i);
        if (p[i] == i)
            continue;
        if (used[i])
            continue;

        cnt ++;
        used[i] = cnt;
        int v = p[i];
        l[cnt] = i;
        while(v != i)
        {
            used[v] = cnt;
            r[cnt] = max(r[cnt], (ll)v);
            v = p[v];
        }
    }

    bef[0] = used[0];
    for (int i = 1; i < n; i ++)
    {
        bef[i] = bef[i - 1];
        if (used[i] != 0)
            bef[i] = used[i];
    }

    aft[n - 1] = used[n - 1];
    for (int i = n - 2; i >= 0; i --)
    {
        aft[i] = aft[i + 1];
        if (used[i] != 0)
            aft[i] = used[i];
    }

    for (int i = 0; i < n; i ++)
        for (int j = 0; j < n; j ++)
            dp[i][j] = inf;

    dp[s][s] = 0;
    if (used[s] != 0)
        dp[l[used[s]]][r[used[s]]] = 0;
    for (int len = 1; len <= n; len ++)
    {
        for (int i = 0; i < n - len + 1; i ++)
        {
            int j = i + len - 1;
            if (dp[i][j] == inf)
                continue;
            vector < int > idx;
            if (i != 0 && bef[i - 1] != 0)
                idx.push_back(bef[i - 1]);
            if (j != n - 1 && aft[j + 1] != 0)
                idx.push_back(aft[j + 1]);
            for (int cur : idx)
            {
                int newl = min((ll)i, l[cur]);
                int newr = max((ll)j, r[cur]);

                dp[newl][newr] = min(dp[newl][newr], dp[i][j] + distance(i, j, l[cur], r[cur]));
            }

        }
    }

    int lf = 0;
    int rf = n - 1;
    while(lf < s && used[lf] == 0)
        lf ++;
    while(rf > s && used[rf] == 0)
        rf --;

    ///cout << lf << " " << rf << endl;
    return ans + dp[lf][rf];


}

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