Submission #767065

#	Time	Username	Problem	Language	Result	Execution time	Memory
767065		danikoynov	Ancient Books (IOI17_books)	C++14	42 / 100	111 ms	16264 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];
vector < int > st[maxn];
ll distance(int l, int r, int i, int j)
{
    if (i <= l && j >= r)
    {
        int mx = 1e9;
        for (int idx : st[used[i]])
        {
            if (idx >= l && idx <= r)
            {
                mx = 0;
                break;
            }
            mx = min(mx, abs(idx - l));
            mx = min(mx, abs(idx - r));
        }
        return mx * 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();
    if (n > 1000)
    {
        int cnt = 0;
    ll mx = 0, ans = 0;
    int to = 0;
    for (int i = 0; i < n; i ++)
    {
        if (p[i] == i)
            continue;
            ans = ans + (ll)abs(i - p[i]);
            ///cout << ans << endl;
        if (!used[i])
        {
            if (to < i)
                mx = mx + i - to;
            int v = p[i];
            while(v != i)
            {

                to = max(to, v);
                used[v] = 1;
                v = p[v];
            }
            to = max(to, v);
            used[v] = 1;
        }
    }
	return ans + 2 * mx;
    }
    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;
        r[cnt] = i;
        st[cnt].push_back(i);
        while(v != i)
        {
            st[cnt].push_back(v);
            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;

    /**cout << "-------------" << endl;
    for (int i = 1; i <= cnt; i ++)
        cout << l[i] << " " << r[i] << endl;
    cout << "-------------" << endl;*/
    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;
                ///cout << i << " " << j << " " << dp[i][j] << endl;
            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 p = 1; p <= cnt; p ++)
                    idx.push_back(p);
            for (int cur : idx)
            {
                int newl = min((ll)i, l[cur]);
                int newr = max((ll)j, r[cur]);
                if (dp[newl][newr] > dp[i][j] + distance(i, j, l[cur], r[cur]))
                {
                    dp[newl][newr] = dp[i][j] + distance(i, j, l[cur], r[cur]);
                    ///cout << "to " << newl << " " << newr << endl;
                }
                ///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 << dp[lf][rf] << endl;
    ///cout << lf << " " << rf << endl;
    return ans + dp[lf][rf];


}

Compilation message (stderr)

books.cpp: In function 'long long int minimum_walk(std::vector<int>, int)':
books.cpp:46:9: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
   46 |         if (p[i] == i)
      |         ^~
books.cpp:48:13: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
   48 |             ans = ans + (ll)abs(i - p[i]);
      |             ^~~
books.cpp:41:13: warning: unused variable 'cnt' [-Wunused-variable]
   41 |         int cnt = 0;
      |             ^~~

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