Submission #734840

#	Time	Username	Problem	Language	Result	Execution time	Memory
734840		Nelt	Xor Sort (eJOI20_xorsort)	C++17	100 / 100	8 ms	1492 KiB

xorsort

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,avx2,fma")

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

/* DEFINES */
#define S second
#define F first
#define ll long long
#define ull unsigned long long
#define ld long double
#define npos ULLONG_MAX
#define INF LLONG_MAX
#define vv(a) vector<a>
#define pp(a, b) pair<a, b>
#define pq(a) priority_queue<a>
#define qq(a) queue<a>
#define ss(a) set<a>
#define mm(a, b) map<a, b>
#define ump(a, b) unordered_map<a, b>
#define sync                      \
    ios_base::sync_with_stdio(0); \
    cin.tie(0);                   \
    cout.tie(0);
#define elif else if
#define endl "\n"
#define allc(a) begin(a), end(a)
#define all(a) a, a + sizeof(a) / sizeof(a[0])
#define pb push_back
#define logi(a) __lg(a)
#define sqrt(a) sqrtl(a)
#define mpr make_pair
#define ins insert
using namespace std;
using namespace __gnu_pbds;
using namespace __cxx11;
typedef char chr;
typedef basic_string<chr> str;
template <typename T, typename key = less<T>>
using ordered_set = tree<T, null_type, key, rb_tree_tag, tree_order_statistics_node_update>;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const ll N = 1005;
vv(pp(ll, ll)) ans;
ll a[N];
void solve()
{
    ll n, s;
    cin >> n >> s;
    for (ll i = 1; i <= n; i++)
        cin >> a[i];
    if (s == 2)
    {
        for (ll bit = 19; bit >= 0; bit--)
        {
            for (ll i = 1; i < n; i++)
            {
                if ((a[i] >> bit & 1) and !(a[i + 1] >> bit & 1))
                    ans.pb(mpr(i + 1, i)), a[i + 1] ^= a[i];
                if ((a[i] >> bit & 1) and (a[i + 1] ^ a[i]) < a[i])
                    ans.pb(mpr(i, i + 1)), a[i] ^= a[i + 1];
            }
        }
    }
    else
    {
        ll b[n + 1];
        for (ll i = 1; i <= n; i++)
            b[i] = a[i];
        ll last = 0;
        for (ll i = n; i > 1; i--)
        {
            ll ind = 1;
            for (ll j = 1; j <= i; j++)
                if ((a[j] ^ last) > (a[ind] ^ last))
                    ind = j;
            for (ll j = 1; j <= i; j++)
                if (j < n)
                    ans.pb(mpr(j, j + 1)), a[j] ^= a[j + 1];
            for (ll j = ind + 1; j <= i; j++)
                ans.pb(mpr(j, j - 1)), a[j] ^= a[j - 1];
            for (ll j = ind - 1; j > 1; j--)
                ans.pb(mpr(j - 1, j)), a[j - 1] ^= a[j];
            last = a[i];
        }
        a[1] ^= a[2];
        ans.pb(mpr(1, 2));
        // for (ll i = 1; i <= n; i++)
        //     cout << a[i] << " \n"[i == n];
    }
    assert(is_sorted(a + 1, a + n + 1) and ans.size() <= 40000);
    cout << ans.size() << endl;
    for (auto [a, b] : ans)
        cout << a << ' ' << b << endl;
}
/*

*/
int main()
{
    sync
        // precomp();
        ll t = 1;
    // cin >> t;
    for (ll i = 1; i <= t; i++)
        // cout << "Case #" << i << ": ",
        solve();
    cerr << "\nTime elapsed : " << clock() * 1000.0 / CLOCKS_PER_SEC << " ms\n";
}

Compilation message (stderr)

xorsort.cpp: In function 'void solve()':
xorsort.cpp:68:12: warning: variable 'b' set but not used [-Wunused-but-set-variable]
   68 |         ll b[n + 1];
      |            ^

• Subtask 1: 25 / 25
• Subtask 2: 35 / 35
• Subtask 3: 40 / 40