// 103. Binary Tree Zigzag Level Order Traversal
// https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/description/
// swift
// Definition for a binary tree node.
public class TreeNode {
public var val: Int
public var left: TreeNode?
public var right: TreeNode?
public init(_ val: Int) {
self.val = val
self.left = nil
self.right = nil
}
}
class Solution {
func zigzagLevelOrder(_ root: TreeNode?) -> [[Int]] {
guard root != nil else {
return [[Int]]()
}
func nextLevelResult(_ nodes: [TreeNode], flag: Bool) -> [TreeNode] {
var result = [TreeNode]()
for node in nodes.reversed() {
if flag {
if (node.left != nil) {
result.append(node.left!)
}
if (node.right != nil) {
result.append(node.right!)
}
} else {
if (node.right != nil) {
result.append(node.right!)
}
if (node.left != nil) {
result.append(node.left!)
}
}
}
return result
}
var result = [[TreeNode]]()
var temp = [root!]
var flag = false
while temp.count > 0 {
result .append(temp)
temp = nextLevelResult(temp, flag: flag)
flag = !flag
}
return result.map { nodes in
nodes.map { node in
node.val
}
}
}
}
