Split in Three

input/code.cpp: In function 'int main()':
input/code.cpp:27:12: warning: unused variable 'tot' [-Wunused-variable]
     int n, tot, look, ans[101];
            ^~~
input/code.cpp:27:17: warning: unused variable 'look' [-Wunused-variable]
     int n, tot, look, ans[101];
                 ^~~~

#include <bits/stdc++.h>

using namespace std;

#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define per(i, a, b) for (int i = a - 1; i >= (b); --i)
#define trav(a, x) for (auto &a : x)

#define all(x) x.begin(), x.end()
#define sz(x) x.size()
#define pb push_back

#define umap unordered_map
#define uset unordered_set
#define INF 1000000000

typedef pair<int, int> ii;
typedef pair<int, ii> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef long long ll;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(NULL);

    int n, tot, look, ans[101];
    pair<int, vi> groups[3];
    groups[0].first = groups[1].first = groups[2].first = 0;
    memset(ans, 0, sizeof(ans));
    cin >> n;
    if (n % 3 == 1) {
        cout << "IMPOSSIBLE"<<endl;
        return 0;
    }

    for (int i = n; i > 0; i -= 3) {
        groups[0].second.pb(i - 1);
        groups[1].second.pb(i);
        if (i != 2) groups[2].second.pb(i - 2);
        groups[0].first += i - 1;
        groups[1].first += i;
        if (i != 2) groups[2].first += i - 2;
        sort(groups, groups + 3);
    }
    
    rep(i,0,3) {
        trav(num,groups[i].second)ans[num]=i+1;
    }
    rep(i,1,n+1)cout<<ans[i]<<' ';
    return 0;
}

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