830A - Office Keys - CodeForces Solution

#include "bits/stdc++.h"
using namespace std;

#define int long long

void solve()
{
    int n, k, pos;
    cin >> n >> k >> pos;
    vector<int> a(n), b(k);
    for (int &x : a)
        cin >> x;
    for (int &x : b)
        cin >> x;

    sort(a.begin(), a.end());
    sort(b.begin(), b.end());

    auto check = [&](int mx)
    {
        vector<int> vis(k);

        // left
        for(int i = 0; i < n; ++i)
        {
            if(a[i] >= pos) break;
            int ans = -1;
            for(int j = 0; j < k; ++j)
            {
                if(vis[j]) continue;
                int dis = max(0LL, a[i] - b[j]);
                if(b[j] > pos) dis = b[j] - pos;
                if(2 * dis + pos - a[i] <= mx)
                {
                    ans = j;
                    break;
                }
            }
            if(ans == -1) return false;
            vis[ans] = 1;
        }


        // right
        for(int i = n - 1; i >= 0; --i)
        {
            if(a[i] < pos) break;
            int ans = -1;
            for(int j = k - 1; j >= 0; --j)
            {
                if(vis[j]) continue;
                int dis = max(0LL, b[j] - a[i]);
                if(b[j] < pos) dis = pos - b[j];
                if(2 * dis + a[i] - pos <= mx)
                {
                    ans = j;
                    break;
                }
            }
            if(ans == -1) return false;
            vis[ans] = 1;
        }

        return true;
    };

    int lo = 0, hi = 2e9, md, ans = -1;
    while(lo <= hi)
    {
        md = (lo + hi) >> 1;
        if(check(md))
            hi = md - 1, ans = md;
        else
            lo = md + 1;
    }

    assert(ans != -1);

    cout << ans << '\n';
    
}

int32_t main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int tc = 1;
    // cin >> tc;
    for (int i = 1; i <= tc; ++i)
        solve();
}