Omenat

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;

#define M 1000000007

map<pair<int, int>, int> mp; 
set<pair<int, int>> vis;

int solve(int one, int two) {
    if (one < 0) return -1e9;
    if (two < 0) return -1e9;
    if (one <= 0 && two <= 0) {
        return 0;
    }
    if (vis.find(make_pair(one, two)) != vis.end()) {
        return mp[{one, two}];
    }
    int ans = 0;
    ans = max(ans, solve(one - 3, two) + 3);
    ans = max(ans, solve(one - 1, two - 1) + 2);
    ans = max(ans, solve(one, two - 3) + 3);
    mp[{one, two}] = ans;
    vis.insert({one, two});
    return ans;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    int zero = 0;
    int one = 0;
    int two = 0;

    for (int i = 0; i < n; ++i) {
        int x;
        cin >> x;
        if (x % 3 == 0) zero++;
        if (x % 3 == 1) one++;
        if (x % 3 == 2) two++;
    }

    int ans = zero;

    while (two > 12) {
        ans += 3;
        two -= 3;
    }
    while (one > 12) {
        ans += 3;
        one -= 3;
    }

    ans += solve(one, two);

    cout << ans << "\n";

    return 0;
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 1

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 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: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED

Test 16

Group: 3

Verdict: ACCEPTED

Test 17

Group: 3

Verdict: ACCEPTED

Test 18

Group: 3

Verdict: ACCEPTED