Magic Grid【构造行列异或和相同】

Let us define a magic grid to be a square matrix of integers of size n×n, satisfying the following conditions.
All integers from 0 to (n2−1) inclusive appear in the matrix exactly once.
Bitwise XOR of all elements in a row or a column must be the same for each row and column.
You are given an integer n which is a multiple of 4. Construct a magic grid of size n×n.

Input
The only line of input contains an integer n (4≤n≤1000). It is guaranteed that n is a multiple of 4.

Output
Print a magic grid, i.e. n lines, the i-th of which contains n space-separated integers, representing the i-th row of the grid.
If there are multiple answers, print any. We can show that an answer always exists.

Examples
inputCopy
4
outputCopy
8 9 1 13
3 12 7 5
0 2 4 11
6 10 15 14
inputCopy
8
outputCopy
19 55 11 39 32 36 4 52
51 7 35 31 12 48 28 20
43 23 59 15 0 8 16 44
3 47 27 63 24 40 60 56
34 38 6 54 17 53 9 37
14 50 30 22 49 5 33 29
2 10 18 46 41 21 57 13
26 42 62 58 1 45 25 61

Note
In the first example, XOR of each row and each column is 13.
In the second example, XOR of each row and each column is 60.

#include <bits/stdc++.h>
using namespace std;
#define maxn 1010
typedef long long ll;
int a[maxn][maxn];
int main(){
	int n; scanf("%d",&n);
	for(int i=0;i<n;i++){
		for(int j=0;j<n;j++) a[i][j]=(n/4*(i/4)+j/4)*16+i%4*4+j%4;
	}
	for(int i=0;i<n;i++){
		for(int j=0;j<n;j++){
			if(j==0) printf("%d",a[i][j]);
			else printf(" %d",a[i][j]);
		} 
		puts("");
	}
	return 0;
}