Ratsun reitit

#include <bits/stdc++.h>

using namespace std;

int size;
vector<int> arr;

bool o(int x, int y){
	return !(x == 0 && y == 0) && x >= 0 && y >= 0 && x < size && y < size && !arr[size*y+x];
}

pair<int,int> d[] = {make_pair(-1,-2), make_pair(1,-2), make_pair(2,-1), make_pair(2, 1), make_pair(1,2), make_pair(-1,2), make_pair(-2,1), make_pair(-2, -1)};

vector<pair<int,int>> a(int x, int y, int t){
	vector<pair<int,int>> p;

	for(pair<int,int> z : d){
		int nx = x+z.first, ny = y+z.second;
		if(o(nx, ny)){
			arr[size*ny+nx] = t;
			p.push_back(make_pair(nx, ny));
		}
	}

	return p;
}

int main(){
	cin >> size;
	arr.resize(size*size);

	int cnt = 1;
	vector<pair<int,int>> nodes = a(0, 0, cnt);
	while(nodes.size() > 0){
		cnt++;
		vector<pair<int,int>> new_nodes;

		for(pair<int,int> node : nodes){
			for(pair<int,int> new_node : a(node.first, node.second, cnt)){
				new_nodes.push_back(new_node);
			}
		}
		nodes = new_nodes;
	}

	for(int y = 0; y < size; y++){
		for(int x = 0; x < size; x++){
			cout << arr[size*y+x] << (x == size-1? '\n' : ' ');
		}
	}
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: ACCEPTED

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 1, 2, 3

Verdict: ACCEPTED

Test 6

Group: 1, 2, 3

Verdict: ACCEPTED

Test 7

Group: 1, 2, 3

Verdict: ACCEPTED

Test 8

Group: 2, 3

Verdict: ACCEPTED

Test 9

Group: 2, 3

Verdict: ACCEPTED

Test 10

Group: 2, 3

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED