Given a positive integer n
, generate an n x n
matrix
filled with elements from 1
to n2
in spiral order.
Example 1:
Input: n = 3 Output: [[1,2,3],[8,9,4],[7,6,5]]
Example 2:
Input: n = 1 Output: [[1]]
Constraints:
1 <= n <= 20
Related Topics:
Array
Similar Questions:
// OJ: https://leetcode.com/problems/spiral-matrix-ii/
// Author: github.com/lzl124631x
// Time: O(N^2)
// Space: O(1)
class Solution {
public:
vector<vector<int>> generateMatrix(int n) {
vector<vector<int>> ans(n, vector<int>(n));
for (int i = 0, d = 1; i < n / 2; ++i) {
int len = n - 2 * i - 1;
for (int j = 0; j < len; ++j) ans[i][i + j] = d++;
for (int j = 0; j < len; ++j) ans[i + j][n - i - 1] = d++;
for (int j = 0; j < len; ++j) ans[n - i - 1][n - i - j - 1] = d++;
for (int j = 0; j < len; ++j) ans[n - i - j - 1][i] = d++;
}
if (n % 2) ans[n / 2][n / 2] = n * n;
return ans;
}
};