• Time:O(n^2)
• Space:O(n^2)

C++

``````class Solution {
public:
vector<vector<int>> generateMatrix(int n) {
vector<vector<int>> ans(n, vector<int>(n));
int count = 1;

for (int min = 0; min < n / 2; ++min) {
const int max = n - min - 1;
for (int i = min; i < max; ++i)
ans[min][i] = count++;
for (int i = min; i < max; ++i)
ans[i][max] = count++;
for (int i = max; i > min; --i)
ans[max][i] = count++;
for (int i = max; i > min; --i)
ans[i][min] = count++;
}

if (n & 1)
ans[n / 2][n / 2] = count;

return ans;
}
};
``````

JAVA

``````class Solution {
public int[][] generateMatrix(int n) {
int[][] ans = new int[n][n];
int count = 1;

for (int min = 0; min < n / 2; ++min) {
final int max = n - min - 1;
for (int i = min; i < max; ++i)
ans[min][i] = count++;
for (int i = min; i < max; ++i)
ans[i][max] = count++;
for (int i = max; i > min; --i)
ans[max][i] = count++;
for (int i = max; i > min; --i)
ans[i][min] = count++;
}

if (n % 2 == 1)
ans[n / 2][n / 2] = count;

return ans;
}
}
``````

Python

``````class Solution:
def generateMatrix(self, n: int) -> List[List[int]]:
ans = [[0] * n for _ in range(n)]
count = 1

for min in range(n // 2):
max = n - min - 1
for i in range(min, max):
ans[min][i] = count
count += 1
for i in range(min, max):
ans[i][max] = count
count += 1
for i in range(max, min, -1):
ans[max][i] = count
count += 1
for i in range(max, min, -1):
ans[i][min] = count
count += 1

if n & 1:
ans[n // 2][n // 2] = count

return ans
``````