[Swift]LeetCode1104. 二叉樹尋路 | Path In Zigzag Labelled Binary Tree

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In an infinite binary tree where every node has two children, the nodes are labelled in row order.

In the odd numbered rows (ie., the first, third, fifth,...), the labelling is left to right, while in the even numbered rows (second, fourth, sixth,...), the labelling is right to left.

Given the label of a node in this tree, return the labels in the path from the root of the tree to the node with that label.

Example 1:

Input: label = 14
Output: [1,3,4,14]

Example 2:

Input: label = 26
Output: [1,2,6,10,26]

Constraints:

• 1 <= label <= 10^6

---

在一棵無限的二叉樹上，每一個節點都有兩個子節點，樹中的節點 逐行 依次按 「之」 字形進行標記。

以下圖所示，在奇數行（即，第一行、第三行、第五行……）中，按從左到右的順序進行標記；

而偶數行（即，第二行、第四行、第六行……）中，按從右到左的順序進行標記。

給你樹上某一個節點的標號 label，請你返回從根節點到該標號爲 label 節點的路徑，該路徑是由途經的節點標號所組成的。

示例 1：

輸入：label = 14
輸出：[1,3,4,14]

示例 2：

輸入：label = 26
輸出：[1,2,6,10,26]

提示：

• 1 <= label <= 10^6

---

Runtime: 4 ms

Memory Usage: 20.5 MB

 1 class Solution {
 2     func pathInZigZagTree(_ label: Int) -> [Int] {
 3         var ret:[Int] = [Int]()
 4         var cur:Int = label
 5         while(true)
 6         {
 7             ret.insert(cur,at:0)
 8             if cur == 1 {break}
 9             cur /= 2
10             let h:Int = highestOneBit(cur)
11             cur ^= h-1
12         }
13         return ret
14     }
15     
16     func highestOneBit(_ i:Int) -> Int
17     {
18         var i = i
19         // HD, Figure 3-1
20         i |= (i >>  1)
21         i |= (i >>  2)
22         i |= (i >>  4)
23         i |= (i >>  8)
24         i |= (i >> 16)
25         return i - (i >> 1)
26     }
27 }

---

8ms 

 1 class Solution {
 2     func pathInZigZagTree(_ label: Int) -> [Int] {
 3         var result = [Int]()
 4         var log = 1
 5         while log <= label {
 6             log <<= 1
 7         }
 8         var label = label 
 9         while label >= 1 {
10             result.append(label)
11             label = log + log / 2 - label - 1
12             label /= 2
13             log /= 2
14         }
15         return result.reversed()
16     }
17 }

---

316ms

 1 class Solution {
 2     func pathInZigZagTree(_ label: Int) -> [Int] {
 3         var level = 1 
 4         var arr = [Int]()
 5         
 6         outer: while true {
 7             let left = Int(pow(2.0, Double(level-1)))
 8             let right = Int(pow(2.0, Double(level))) - 1
 9 
10             if level % 2 == 1 {
11                 for v in left...right {
12                     if v == label { 
13                         arr.append(v)
14                         break outer
15                     }
16                     arr.append(v)
17                 }
18             } else {
19                 for v in stride(from:right, through: left, by: -1) {
20                     if v == label { 
21                         arr.append(v)
22                         break outer
23                     }
24                     arr.append(v)
25                 }
26             }
27             level += 1
28         }
29         
30         var idx = arr.count - 1
31         var result = [Int]()
32         
33         while idx > 0 {
34             result.append(arr[idx])
35             idx = (idx - 1) / 2
36         }
37         result.append(arr[0])
38         return result.reversed()
39     }
40 }

---

536ms

 1 class Solution {
 2     func pathInZigZagTree(_ label: Int) -> [Int] {
 3         var tree = [Int]()
 4         var prevPow = 1
 5         var reverse = false
 6         outer: for i in 1...20 {
 7             let num = Int(pow(2, Double(i)))
 8             if reverse {
 9                 for j in stride(from: num - 1, through: prevPow, by: -1) {
10                     tree.append(j)
11                     if j == label { break outer }
12                 }
13             } else {
14                 for j in stride(from: prevPow, to: num, by: 1) {
15                     tree.append(j)
16                     if j == label { break outer }
17                 }
18             }
19             prevPow = num
20             reverse = !reverse
21         }
22         var res = [Int]()
23         var i = tree.count - 1
24         while i > 0 {
25             res.append(tree[i])
26             i = (i - 1)/2
27         }
28         res.append(tree[i])
29         return Array(res.reversed())
30     }
31 }