Submission #10,709

2024-04-10 09:44:25

cpp17

Accepted 100/100

145ms

37584 KiB

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

const int MAXN = 200'001;

int a[MAXN], mine;
bool vis[MAXN];
vector<int> c;
vector<int> g[MAXN];
vector<pair<int, int>> ans;

void dfs(int u) {
    vis[u] = true;
    mine = min(mine, u);
    c.emplace_back(u);
    for (int v : g[u]) {
        if (!vis[v]) {
            dfs(v);
        }
    }
}

int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    int n; cin >> n;
    vector<int> comp;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        comp.emplace_back(a[i]);
    }
    sort(comp.begin(), comp.end());
    comp.erase(unique(comp.begin(), comp.end()), comp.end());
    for (int i = 1; i <= n; i++) a[i] = lower_bound(comp.begin(), comp.end(), a[i])-comp.begin();
    for (int i = 1; i <= n; i++) {
        if (a[i] != a[n-i+1]) {
            g[a[i]].emplace_back(a[n-i+1]);
        }
    }

    for (int i = 0; i < comp.size(); i++) {
        if (!vis[i]) {
            mine = 1e9;
            dfs(i);
            for (int j : c) {
                if (j != mine) {
                    ans.emplace_back(comp[j], comp[mine]);
                }
            }
            c.clear();
        }
    }

    cout << ans.size() << "\n";
    for (auto [a, b] : ans) cout << a << " " << b << "\n";
    return 0;
}

	Sum	Test	Verdict	Time	Memory
subtask1	0/0
		1	Accepted	6ms	11260 KiB
		2	Accepted	64ms	19156 KiB
subtask2	9/9
		3	Accepted	7ms	11840 KiB
		4	Accepted	7ms	12172 KiB
		5	Accepted	7ms	12248 KiB
		6	Accepted	7ms	12596 KiB
		7	Accepted	7ms	12560 KiB
subtask3	14/14
		8	Accepted	7ms	12400 KiB
		9	Accepted	7ms	12400 KiB
		10	Accepted	7ms	12656 KiB
		11	Accepted	6ms	12876 KiB
		12	Accepted	7ms	12824 KiB
		13	Accepted	7ms	13080 KiB
subtask4	25/25
		14	Accepted	6ms	13176 KiB
		15	Accepted	7ms	13456 KiB
		16	Accepted	8ms	13584 KiB
		17	Accepted	8ms	13788 KiB
		18	Accepted	8ms	13756 KiB
		19	Accepted	8ms	13740 KiB
		20	Accepted	7ms	14000 KiB
		21	Accepted	7ms	14164 KiB
subtask5	22/22
		22	Accepted	90ms	25352 KiB
		23	Accepted	107ms	37584 KiB
		24	Accepted	104ms	37476 KiB
		25	Accepted	93ms	25460 KiB
		26	Accepted	90ms	25436 KiB
		27	Accepted	105ms	36436 KiB
		28	Accepted	107ms	36440 KiB
		29	Accepted	92ms	25444 KiB
		30	Accepted	89ms	25436 KiB
		31	Accepted	104ms	37028 KiB
		32	Accepted	101ms	37020 KiB
		33	Accepted	90ms	25432 KiB
		34	Accepted	86ms	25452 KiB
		35	Accepted	100ms	31368 KiB
		36	Accepted	103ms	34604 KiB
		37	Accepted	90ms	25640 KiB
subtask6	30/30
		38	Accepted	6ms	14264 KiB
		39	Accepted	64ms	22152 KiB
		40	Accepted	7ms	11840 KiB
		41	Accepted	7ms	12172 KiB
		42	Accepted	7ms	12248 KiB
		43	Accepted	7ms	12596 KiB
		44	Accepted	7ms	12560 KiB
		45	Accepted	7ms	12400 KiB
		46	Accepted	7ms	12400 KiB
		47	Accepted	7ms	12656 KiB
		48	Accepted	6ms	12876 KiB
		49	Accepted	7ms	12824 KiB
		50	Accepted	7ms	13080 KiB
		51	Accepted	6ms	13176 KiB
		52	Accepted	7ms	13456 KiB
		53	Accepted	8ms	13584 KiB
		54	Accepted	8ms	13788 KiB
		55	Accepted	8ms	13756 KiB
		56	Accepted	8ms	13740 KiB
		57	Accepted	7ms	14000 KiB
		58	Accepted	7ms	14164 KiB
		59	Accepted	90ms	25352 KiB
		60	Accepted	107ms	37584 KiB
		61	Accepted	104ms	37476 KiB
		62	Accepted	93ms	25460 KiB
		63	Accepted	90ms	25436 KiB
		64	Accepted	105ms	36436 KiB
		65	Accepted	107ms	36440 KiB
		66	Accepted	92ms	25444 KiB
		67	Accepted	89ms	25436 KiB
		68	Accepted	104ms	37028 KiB
		69	Accepted	101ms	37020 KiB
		70	Accepted	90ms	25432 KiB
		71	Accepted	86ms	25452 KiB
		72	Accepted	100ms	31368 KiB
		73	Accepted	103ms	34604 KiB
		74	Accepted	90ms	25640 KiB
		75	Accepted	136ms	28840 KiB
		76	Accepted	111ms	25900 KiB
		77	Accepted	52ms	19768 KiB
		78	Accepted	112ms	25924 KiB
		79	Accepted	86ms	22224 KiB
		80	Accepted	82ms	18036 KiB
		81	Accepted	82ms	18044 KiB
		82	Accepted	82ms	18044 KiB
		83	Accepted	145ms	28840 KiB
		84	Accepted	59ms	19784 KiB
		85	Accepted	90ms	22232 KiB
		86	Accepted	90ms	18044 KiB
		87	Accepted	90ms	18048 KiB
		88	Accepted	90ms	18036 KiB
		89	Accepted	87ms	18044 KiB