Submission #654845

#	Time	Username	Problem	Language	Result	Execution time	Memory
654845		benjaminkleyn	Arranging Shoes (IOI19_shoes)	C++17	100 / 100	118 ms	7736 KiB

shoes

#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx,avx2,fma")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int t[800000] = {0};
void update(int v, int tl, int tr, int idx, int val)
{
    if (tl == tr)
    {
        t[v] = val;
        return;
    }

    int tm = (tl + tr) / 2;

    if (idx <= tm)
        update(v*2, tl, tm, idx, val);
    else
        update(v*2+1, tm+1, tr, idx, val);

    t[v] = t[v*2] + t[v*2+1];
}

int sum(int v, int tl, int tr, int l, int r)
{
    if (r < l || tr < tl)
        return 0;
    if (tl == l && tr == r)
        return t[v];

    int tm = (tl + tr) / 2;

    return sum(v*2, tl, tm, l, min(r, tm))
         + sum(v*2+1, tm+1, tr, max(l, tm+1), r);
}


long long count_swaps(vector<int> s)
{
    int n = s.size() / 2;
    if (n == 1)
        return s[1] < s[0];

    vector<pair<int,int>> neg, pos;
    for (int i = 0; i < 2 * n; i++)
        if (s[i] < 0) 
            neg.push_back({-s[i],i});
        else 
            pos.push_back({s[i],i});

    sort(neg.begin(), neg.end());
    sort(pos.begin(), pos.end());

    vector<pair<int,int>> pairs(n);
    for (int i = 0; i < n; i++)
        pairs[i] = {neg[i].second, pos[i].second};

    sort(pairs.begin(), pairs.end(), [](const pair<int,int> &a, const pair<int,int> &b) 
            {return min(a.first,a.second) < min(b.first,b.second);});

    ll res = 0;

    for (auto [i, j] : pairs)
    {
        if (i < j)
        {
            // j must move to the right of i.
            res += j - i - 1 - sum(1, 0, 2*n-1, i+1, j-1);
            update(1, 0, 2*n-1, j, 1);
        }
        else
        {
            // i must move to the left of j.
            res += i - j - sum(1, 0, 2*n-1, j+1, i-1);
            update(1, 0, 2*n-1, i, 1);
        }
    }
    
    return res;
}

• Subtask 1: 10 / 10
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 15 / 15
• Subtask 5: 20 / 20
• Subtask 6: 15 / 15