Kolmijako

#include <iostream>
#include <vector>
 
using namespace std;
 
int n;
vector<int> nums;

vector<int> a;
vector<int> b;
vector<int> c;

int ans[101];

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  
  cin>>n;
 
  int x = (n*(n+1)/2-3)/3;

  if ((n-1) % 3 == 0) {
    cout << "IMPOSSIBLE";
  } else {
    nums.resize(n);
    for (int i = 1; i <= n; i++) nums[i-1] = i;

    // Muodostetaan joukko A
    int sum = 0;
    for (int i = nums.size()-1; i >= 0; i--) {
      if (sum+nums[i] <= x) {
        sum += nums[i];
        a.push_back(nums[i]);
        nums[i] = 0;
      }
    }

    for (int i = 0; i < n; i++) {
      if (sum == x) break;
      if (sum + nums[i] <= x) {
        sum += nums[i];
        a.push_back(nums[i]);
        nums[i] = 0;
      }
    }

    // Muodostetaan joukko B
    sum = 0;
    for (int i = nums.size()-1; i >= 0; i--) {
      if (sum+nums[i] <= x+1 && nums[i] > 0) {
        sum += nums[i];
        b.push_back(nums[i]);
        nums[i] = 0;
      }
    }

    for (int i = 0; i < n; i++) {
      if (sum == x+1) break;
      if (sum + nums[i] <= x+1 && nums[i] > 0) {
        sum += nums[i];
        b.push_back(nums[i]);
        nums[i] = 0;
      }
    }

    // Muodostetaan joukko C
    sum = 0;
    for (int i = nums.size()-1; i >= 0; i--) {
      if (sum+nums[i] <= x+2 && nums[i] > 0) {
        sum += nums[i];
        c.push_back(nums[i]);
        nums[i] = 0;
      }
    }

    for (int i = 0; i < n; i++) {
      if (sum == x+2) break;
      if (sum + nums[i] <= x+2 && nums[i] > 0) {
        sum += nums[i];
        c.push_back(nums[i]);
        nums[i] = 0;
      }
    }

    // Tulostetaan vastaus


    for (int i : a) {
      ans[i] = 1;
    }
    for (int i : b) {
      ans[i] = 2;
    }
    for (int i : c) {
      ans[i] = 3;
    }

    for (int i = 1; i <= n; i++) cout << ans[i] << " ";
  }
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 1, 2

Verdict: ACCEPTED

Test 3

Group: 1, 2

Verdict: ACCEPTED

Test 4

Group: 1, 2

Verdict: ACCEPTED

Test 5

Group: 1, 2

Verdict: ACCEPTED

Test 6

Group: 1, 2

Verdict: ACCEPTED

Test 7

Group: 1, 2

Verdict: ACCEPTED

Test 8

Group: 1, 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: ACCEPTED

Test 14

Group: 2

Verdict: ACCEPTED

Test 15

Group: 2

Verdict: ACCEPTED