Odd Matrix

#include <iostream>
#include <vector>

static void fill(std::vector<bool>& b, unsigned n, unsigned pos, unsigned step) {
	for(; n--; pos += step)
		b[pos] = true;
}

static auto odd(unsigned N) {
	std::vector<bool> b(N * N);
	b[0] = true; // base case
	for(unsigned n = 1; n != N; n += 2) {
		fill(b, n, n, N);
		fill(b, n + 2, n + 1, N);
	}
	return b;
}

static auto even(unsigned N) {
	std::vector<bool> b(N * N);
	b[0] = true; // base case
	b[N + 1] = true; // base case
	for(unsigned n = 2; n != N; n += 2) {
		fill(b, n + 1, n, N);
		fill(b, n, n + 1, N);
		b[(n + 1) * (N + 1)] = true;
	}
	return b;
}

static void print(const std::vector<bool>& b, unsigned N) {
	auto gen_odd = [i = 0]() mutable { return i++ * 2 + 1; };
	auto gen_even = [i = 0]() mutable { return i++ * 2 + 2; };
	for(unsigned j = 0, p = 0; j != N; ++j) {
		std::cout << (b[p++] ? gen_odd() : gen_even());
		for(unsigned i = 1; i != N; ++i)
			std::cout << ' ' << (b[p++] ? gen_odd() : gen_even());
		std::cout << '\n';
	}
}

static void testcase() {
	unsigned N;
	std::cin >> N;
	auto b = N % 2 ? odd(N) : even(N);
	print(b, N);
}

int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	std::cin.exceptions(std::ios::failbit | std::ios::badbit);
	unsigned T;
	std::cin >> T;
	while(T--)
		testcase();
}