剪贴板 nkzp9mbk - 洛谷保存站

```cpp
#include <bits/stdc++.h>
#define int long long
using namespace std;
int t, n, m;
signed main() {
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin >> t;
	while (t--) {
		cin >> n >> m;
		if (n == 1 && m == 1) cout << 1 << "\n";
		else if (n == 1 && m > 1) cout << -1 << "\n";
		else if (n % 2 == 1 && m % 2 == 0) cout << -1 << "\n";
		else if (n % 2 == 0) {
			for (int i = 1; i <= n; i++) {
				if (i % 2 == 1) for (int j = 1; j <= m; j++) cout << j << " ";
				else for (int j = m; j >= 1; j--) cout << j << " ";
				cout << "\n";
			}
		} else {
			for (int i = 1; i <= n - 3; i++) {
				if (i % 2 == 1) for (int j = 1; j <= m; j++) cout << j << " ";
				else for (int j = m; j >= 1; j--) cout << j << " ";
				cout << "\n";
			}
			for (int i = 1; i <= m; i++) cout << i << " ";
			cout << "\n";
			for (int i = m / 2 + 1; i <= m; i++) cout << i << " ";
			for (int i = 1; i <= m / 2; i++) cout << i << " ";
			cout << "\n";
			for (int i = m; i >= 2; i--) {
				if (i % 2 == 1) cout << m - (m - i) / 2 << " ";
				else cout << m - (m - i) / 2 - (m / 2 + 1) << " ";
			}
			cout << m / 2 + 1 << " ";
			cout << "\n";
		}
	}
	return 0;
}
```

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