Submission #10,827

2024-04-16 08:24:08

cpp17

Accepted 100/100

194ms

34320 KiB

#include <bits/stdc++.h>
#define int long long
using namespace std;

vector<vector<int>> g;
vector<int> color, parent, depth;

int get_root(int u) {
  if (u == parent[u]) return u;
  return parent[u] = get_root(parent[u]);
}

vector<array<int, 2>> sol;

void merge(int u, int v, bool init) {
  u = get_root(u), v = get_root(v);
  if (u == v) return;
  if (!init) assert(color[u] != color[v]);
  if (depth[u] < depth[v]) swap(u, v);
  if (depth[u] == depth[v]) depth[u]++;
  int c1 = min(color[u], color[v]);
  int c2 = max(color[u], color[v]);
  color[u] = c1;
  parent[v] = u;
  if (init) return;
  sol.push_back({c2, c1});
}

signed main() {
  ios::sync_with_stdio(0), cin.tie(0);
  int n;
  cin >> n;
  parent.resize(n + 1);
  iota(parent.begin(), parent.end(), 0);
  depth.assign(n + 1, 1);
  color.resize(n + 1);
  map<int, int> col_map;
  for (int i = 1; i <= n; i++) {
    cin >> color[i];
    if (col_map.count(color[i])) {
      merge(col_map[color[i]], i, true);
    }
    else {
      col_map[color[i]] = i;
    }
  }

  for (int i = 1; i <= n; i++) {
    int j = n - i + 1;
    if (j <= i) break;
    merge(i, j, false);
  }

  cout << sol.size() << endl;
  for (auto [a, b] : sol) cout << a << ' ' << b << '\n';
}

	Sum	Test	Verdict	Time	Memory
subtask1	0/0
		1	Accepted	3ms	1700 KiB
		2	Accepted	75ms	14608 KiB
subtask2	9/9
		3	Accepted	3ms	2396 KiB
		4	Accepted	3ms	2492 KiB
		5	Accepted	3ms	2768 KiB
		6	Accepted	3ms	2652 KiB
		7	Accepted	3ms	2940 KiB
subtask3	14/14
		8	Accepted	3ms	2924 KiB
		9	Accepted	2ms	3004 KiB
		10	Accepted	3ms	3132 KiB
		11	Accepted	3ms	3368 KiB
		12	Accepted	3ms	3572 KiB
		13	Accepted	3ms	3660 KiB
subtask4	25/25
		14	Accepted	3ms	3660 KiB
		15	Accepted	3ms	3988 KiB
		16	Accepted	4ms	4436 KiB
		17	Accepted	4ms	4692 KiB
		18	Accepted	4ms	4472 KiB
		19	Accepted	4ms	4616 KiB
		20	Accepted	4ms	4568 KiB
		21	Accepted	4ms	4648 KiB
subtask5	22/22
		22	Accepted	123ms	28324 KiB
		23	Accepted	129ms	30376 KiB
		24	Accepted	134ms	30320 KiB
		25	Accepted	119ms	28252 KiB
		26	Accepted	122ms	28292 KiB
		27	Accepted	125ms	30476 KiB
		28	Accepted	128ms	30556 KiB
		29	Accepted	115ms	28488 KiB
		30	Accepted	103ms	28656 KiB
		31	Accepted	109ms	30744 KiB
		32	Accepted	114ms	30752 KiB
		33	Accepted	97ms	28704 KiB
		34	Accepted	83ms	28704 KiB
		35	Accepted	98ms	30904 KiB
		36	Accepted	100ms	30900 KiB
		37	Accepted	86ms	28696 KiB
subtask6	30/30
		38	Accepted	3ms	4824 KiB
		39	Accepted	82ms	17568 KiB
		40	Accepted	3ms	2396 KiB
		41	Accepted	3ms	2492 KiB
		42	Accepted	3ms	2768 KiB
		43	Accepted	3ms	2652 KiB
		44	Accepted	3ms	2940 KiB
		45	Accepted	3ms	2924 KiB
		46	Accepted	2ms	3004 KiB
		47	Accepted	3ms	3132 KiB
		48	Accepted	3ms	3368 KiB
		49	Accepted	3ms	3572 KiB
		50	Accepted	3ms	3660 KiB
		51	Accepted	3ms	3660 KiB
		52	Accepted	3ms	3988 KiB
		53	Accepted	4ms	4436 KiB
		54	Accepted	4ms	4692 KiB
		55	Accepted	4ms	4472 KiB
		56	Accepted	4ms	4616 KiB
		57	Accepted	4ms	4568 KiB
		58	Accepted	4ms	4648 KiB
		59	Accepted	123ms	28324 KiB
		60	Accepted	129ms	30376 KiB
		61	Accepted	134ms	30320 KiB
		62	Accepted	119ms	28252 KiB
		63	Accepted	122ms	28292 KiB
		64	Accepted	125ms	30476 KiB
		65	Accepted	128ms	30556 KiB
		66	Accepted	115ms	28488 KiB
		67	Accepted	103ms	28656 KiB
		68	Accepted	109ms	30744 KiB
		69	Accepted	114ms	30752 KiB
		70	Accepted	97ms	28704 KiB
		71	Accepted	83ms	28704 KiB
		72	Accepted	98ms	30904 KiB
		73	Accepted	100ms	30900 KiB
		74	Accepted	86ms	28696 KiB
		75	Accepted	192ms	34068 KiB
		76	Accepted	144ms	22648 KiB
		77	Accepted	57ms	17056 KiB
		78	Accepted	137ms	22600 KiB
		79	Accepted	101ms	17576 KiB
		80	Accepted	131ms	26284 KiB
		81	Accepted	133ms	26132 KiB
		82	Accepted	142ms	26188 KiB
		83	Accepted	194ms	34320 KiB
		84	Accepted	63ms	17120 KiB
		85	Accepted	111ms	17588 KiB
		86	Accepted	144ms	26668 KiB
		87	Accepted	144ms	26664 KiB
		88	Accepted	143ms	26792 KiB
		89	Accepted	140ms	26792 KiB