0054-spiral-matrix.swift

/**
 * Question Link: https://leetcode.com/problems/spiral-matrix/
 */

 class Solution {
    func spiralOrder(_ matrix: [[Int]]) -> [Int] {
        var res = [Int]()
        var l = 0
        var r = matrix[0].count
        var t = 0
        var b = matrix.count
        while l < r && t < b {
            for i in l..<r {
                res.append(matrix[t][i])
            }
            t += 1
            for i in t..<b {
                res.append(matrix[i][r - 1])
            }
            r -= 1
            if !(l < r && t < b) {
                break
            }
            for i in stride(from: r - 1, to: l - 1, by: -1) {
                res.append(matrix[b - 1][i])
            }
            b -= 1
            for i in stride(from: b - 1, to: t - 1, by: -1) {
                res.append(matrix[i][l])
            }
            l += 1
        }
        return res
    }
}