Submission #675586

#	Time	Username	Problem	Language	Result	Execution time	Memory
675586		benjaminkleyn	Gondola (IOI14_gondola)	C++17	60 / 100	19 ms	5332 KiB

gondola

#include <bits/stdc++.h>
#include "gondola.h"
using namespace std;
typedef long long ll;

unordered_map<int,int> cnt;
int valid(int n, int inputSeq[])
{
    cnt.clear();
    for (int i = 0; i < n; i++)
    {
        cnt[inputSeq[i]]++;
        if (cnt[inputSeq[i]] > 1)
            return 0;
    }
    int startPos = -1;
    for (int i = 0; i < n; i++)
        if (inputSeq[i] <= n)
        {
            startPos = (i - inputSeq[i] + 1 + n) % n;
            break;
        }
    if (startPos == -1)
        return 1;
    for (int i = 0; i < n; i++)
        if (inputSeq[i] <= n && startPos != (i - inputSeq[i] + 1 + n) % n)
            return 0;
    return 1;
}

int replacement(int n, int gondolaSeq[], int replacementSeq[])
{
    vector<pair<int,int>> r;
    int startPos = 0;
    for (int i = 0; i < n; i++)
        if (gondolaSeq[i] > n)
            r.push_back({gondolaSeq[i], i});
        else
            startPos = (i - gondolaSeq[i] + 1 + n) % n;

    sort(r.begin(), r.end());

    int l = 0;
    int cur_mx = n;
    for (auto [newval, idx] : r)
    {
        int oldval = 1 + (idx - startPos + n) % n;
        while (oldval != newval)
        {
            replacementSeq[l++] = oldval;
            oldval = ++cur_mx;
        }
    }

    return l;
}

const ll mod = 1000000009;
ll binpow(ll b, ll n)
{
    ll res = 1;
    for (; n; n >>= 1, b = b * b % mod)
        if (n & 1)
            res = res * b % mod;
    return res;
}

int countReplacement(int n, int inputSeq[])
{
    if (!valid(n, inputSeq))
        return 0;

    vector<pair<int,int>> r;
    int startPos = -1;
    for (int i = 0; i < n; i++)
        if (inputSeq[i] > n)
            r.push_back({inputSeq[i], i});
        else
            startPos = (i - inputSeq[i] + 1 + n) % n;

    if (startPos == -1)
        return 0; // for now this is too complicated

    sort(r.begin(), r.end());

    ll res = 1;
    int cur_mx = n;

    int cnt = r.size();
    for (auto [newval, idx] : r)
    {
        int oldval = 1 + (idx - startPos + n) % n;
        res = res * binpow(--cnt, newval - 1 - cur_mx) % mod;
        // basically, seq[i] = ++cur_mx for some i until cur_mx = newval - 1.
        cur_mx = newval;
        // and then seq[idx] = ++cur_mx.

        // the first one happens (newval - 1) - cur_mx times
        // and the last one is fixed.
    }

    return res;
}

Compilation message (stderr)

gondola.cpp: In function 'int countReplacement(int, int*)':
gondola.cpp:92:13: warning: unused variable 'oldval' [-Wunused-variable]
   92 |         int oldval = 1 + (idx - startPos + n) % n;
      |             ^~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 10 / 10
• Subtask 4: 5 / 5
• Subtask 5: 10 / 10
• Subtask 6: 20 / 20
• Subtask 7: 5 / 5
• Subtask 8: 0 / 15
• Subtask 9: 0 / 15
• Subtask 10: 0 / 10