59. Spiral Matrix II Medium

1/**
2 * [59] Spiral Matrix II
3 *
4 * Given a positive integer n, generate an n x n matrix filled with elements from 1 to n^2 in spiral order.
5 *  
6 * Example 1:
7 * <img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/spiraln.jpg" style="width: 242px; height: 242px;" />
8 * Input: n = 3
9 * Output: [[1,2,3],[8,9,4],[7,6,5]]
10 *
11 * Example 2:
12 *
13 * Input: n = 1
14 * Output: [[1]]
15 *
16 *  
17 * Constraints:
18 *
19 * 1 <= n <= 20
20 *
21 */
22pub struct Solution {}
23
24// problem: https://leetcode.com/problems/spiral-matrix-ii/
25// discuss: https://leetcode.com/problems/spiral-matrix-ii/discuss/?currentPage=1&orderBy=most_votes&query=
26
27// submission codes start here
28
29impl Solution {
30    pub fn generate_matrix(n: i32) -> Vec<Vec<i32>> {
31        let mut result = vec![vec![0; n as usize]; n as usize];
32
33        let mut top = 0;
34        let mut bottom = n as usize - 1;
35        let mut left = 0;
36        let mut right = n as usize - 1;
37        let mut current = 1;
38
39        while current <= n * n {
40            for i in left..right + 1 {
41                result[top][i] = current;
42                current += 1;
43            }
44            top += 1;
45            for i in top..bottom + 1 {
46                result[i][right] = current;
47                current += 1;
48            }
49            if right == 0 {
50                break;
51            }
52            right -= 1;
53            for i in (left..right + 1).rev() {
54                result[bottom][i] = current;
55                current += 1;
56            }
57            if bottom == 0 {
58                break;
59            }
60            bottom -= 1;
61            for i in (top..bottom + 1).rev() {
62                result[i][left] = current;
63                current += 1;
64            }
65            left += 1;
66        }
67
68        result
69    }
70}
71
72// submission codes end
73
74#[cfg(test)]
75mod tests {
76    use super::*;
77
78    #[test]
79    fn test_59() {
80        let x = Solution::generate_matrix(3);
81        println!("Got {:#?}", x);
82    }
83}
84