值得注意的是最后的输出格式，%-3d是左对齐3位，不足的用空格补齐

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int main() {
	int n;
	scanf("%d", &n);
	int** a = (int**)malloc(sizeof(int*) * n);
	for (int i = 0; i < n; i++)
		a[i] = (int*)malloc(sizeof(int) * n);
	int t = 1;
	int on = 0, down = n, left = 0, right = n;
	while (on < down && left < right) {
		for (int i = on; i < down; i++)//左
			a[i][left] = t++;
		for (int i = left + 1; i < right; i++)//下
			a[down-1][i] = t++;
		for (int i = down - 2; i >= on; i--)//右
			a[i][right-1] = t++;
		for (int i = right - 2; i > left; i--)//上
			a[on][i] = t++;
		on++, down--, left++, right--;
	}
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			printf("%-3d ", a[i][j]);
		}
		printf("\n");
	}
	return 0;
}