59. Spiral Matrix II

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

# @lc code=start
using LeetCode

function generate_matrix(n::Int)::Vector{Vector{Int}}
    mat = [fill(0, n) for _ = 1:n]
    i, j, di, dj = 1, 1, 0, 1

    for k = 1:n*n
        mat[i][j] = k
        if mat[mod1(i + di, n)][mod1(j + dj, n)] != 0
            di, dj = dj, -di
        end

        i += di
        j += dj
    end

    return mat
end
# @lc code=end

generate_matrix (generic function with 1 method)

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