Submission #16,288

2025-04-20 12:11:58

cpp17

Accepted 100/100

428ms

26164 KiB

#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define sz(x) (int)x.size()
map<int, vector<int>> adj;
vector<array<int, 2>> ans;
void add(int a, int b)
{
    if(a==b) return;
    ans.pb({max(a,b),min(a,b)});
}
set<int> vis;
vector<int> curr;
int mini;
void dfs(int cs)
{
    vis.insert(cs);
    curr.push_back(cs);
    mini=min(mini,cs);
    for(int &i:adj[cs])
        if(!vis.count(i)) dfs(i);
}
int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int n; cin>>n;
    vector<int> v(n+1);
    for(int i=1; i<=n; i++)
        cin>>v[i];
    for(int i=1; i<=n/2; i++)
        if(v[i]!=v[n-i+1])
    {
        adj[v[i]].pb(v[n-i+1]);
        adj[v[n-i+1]].pb(v[i]);
    }
    for(int i=1; i<=n; i++)
        if(!vis.count(v[i]))
    {
        mini=1e9+10;
        curr.clear();
        dfs(v[i]);
        for(int &x:curr)
            add(x,mini);
    }
    cout<<sz(ans)<<"\n";
    for(auto [a,b]:ans)
        cout<<a<<" "<<b<<"\n";
}

	Sum	Test	Verdict	Time	Memory
subtask1	0/0
		1	Accepted	1ms	316 KiB
		2	Accepted	135ms	10036 KiB
subtask2	9/9
		3	Accepted	2ms	316 KiB
		4	Accepted	1ms	316 KiB
		5	Accepted	1ms	316 KiB
		6	Accepted	1ms	316 KiB
		7	Accepted	1ms	316 KiB
subtask3	14/14
		8	Accepted	1ms	316 KiB
		9	Accepted	1ms	316 KiB
		10	Accepted	1ms	316 KiB
		11	Accepted	1ms	316 KiB
		12	Accepted	1ms	316 KiB
		13	Accepted	1ms	316 KiB
subtask4	25/25
		14	Accepted	1ms	328 KiB
		15	Accepted	2ms	316 KiB
		16	Accepted	3ms	564 KiB
		17	Accepted	4ms	588 KiB
		18	Accepted	3ms	564 KiB
		19	Accepted	3ms	564 KiB
		20	Accepted	3ms	564 KiB
		21	Accepted	2ms	576 KiB
subtask5	22/22
		22	Accepted	209ms	18936 KiB
		23	Accepted	203ms	26156 KiB
		24	Accepted	221ms	26164 KiB
		25	Accepted	211ms	18848 KiB
		26	Accepted	187ms	18856 KiB
		27	Accepted	174ms	25704 KiB
		28	Accepted	170ms	25704 KiB
		29	Accepted	174ms	18860 KiB
		30	Accepted	166ms	18860 KiB
		31	Accepted	164ms	25920 KiB
		32	Accepted	153ms	25896 KiB
		33	Accepted	156ms	18860 KiB
		34	Accepted	162ms	18860 KiB
		35	Accepted	177ms	22468 KiB
		36	Accepted	165ms	24144 KiB
		37	Accepted	174ms	18984 KiB
subtask6	30/30
		38	Accepted	1ms	508 KiB
		39	Accepted	143ms	10032 KiB
		40	Accepted	2ms	316 KiB
		41	Accepted	1ms	316 KiB
		42	Accepted	1ms	316 KiB
		43	Accepted	1ms	316 KiB
		44	Accepted	1ms	316 KiB
		45	Accepted	1ms	316 KiB
		46	Accepted	1ms	316 KiB
		47	Accepted	1ms	316 KiB
		48	Accepted	1ms	316 KiB
		49	Accepted	1ms	316 KiB
		50	Accepted	1ms	316 KiB
		51	Accepted	1ms	328 KiB
		52	Accepted	2ms	316 KiB
		53	Accepted	3ms	564 KiB
		54	Accepted	4ms	588 KiB
		55	Accepted	3ms	564 KiB
		56	Accepted	3ms	564 KiB
		57	Accepted	3ms	564 KiB
		58	Accepted	2ms	576 KiB
		59	Accepted	209ms	18936 KiB
		60	Accepted	203ms	26156 KiB
		61	Accepted	221ms	26164 KiB
		62	Accepted	211ms	18848 KiB
		63	Accepted	187ms	18856 KiB
		64	Accepted	174ms	25704 KiB
		65	Accepted	170ms	25704 KiB
		66	Accepted	174ms	18860 KiB
		67	Accepted	166ms	18860 KiB
		68	Accepted	164ms	25920 KiB
		69	Accepted	153ms	25896 KiB
		70	Accepted	156ms	18860 KiB
		71	Accepted	162ms	18860 KiB
		72	Accepted	177ms	22468 KiB
		73	Accepted	165ms	24144 KiB
		74	Accepted	174ms	18984 KiB
		75	Accepted	418ms	24228 KiB
		76	Accepted	246ms	13356 KiB
		77	Accepted	64ms	5888 KiB
		78	Accepted	250ms	13352 KiB
		79	Accepted	150ms	7104 KiB
		80	Accepted	196ms	14388 KiB
		81	Accepted	173ms	14384 KiB
		82	Accepted	216ms	14388 KiB
		83	Accepted	428ms	25568 KiB
		84	Accepted	71ms	6576 KiB
		85	Accepted	158ms	7876 KiB
		86	Accepted	190ms	15668 KiB
		87	Accepted	190ms	15668 KiB
		88	Accepted	190ms	15676 KiB
		89	Accepted	165ms	15668 KiB