[Swift]LeetCode847. 訪問全部節點的最短路徑 | Shortest Path Visiting All Nodes

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➤微信公衆號：山青詠芝（shanqingyongzhi）
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An undirected, connected graph of N nodes (labeled 0, 1, 2, ..., N-1) is given as graph.

graph.length = N, and j != i is in the list graph[i] exactly once, if and only if nodes i and j are connected.

Return the length of the shortest path that visits every node. You may start and stop at any node, you may revisit nodes multiple times, and you may reuse edges.

Example 1:

Input: [[1,2,3],[0],[0],[0]]
Output: 4
Explanation: One possible path is [1,0,2,0,3]

Example 2:

Input: [[1],[0,2,4],[1,3,4],[2],[1,2]]
Output: 4
Explanation: One possible path is [0,1,4,2,3]

Note:

1. 1 <= graph.length <= 12
2. 0 <= graph[i].length < graph.length

---

給出 graph 爲有 N 個節點（編號爲 0, 1, 2, ..., N-1）的無向連通圖。 

graph.length = N，且只有節點 i 和 j 連通時，j != i 在列表 graph[i] 中剛好出現一次。

返回可以訪問全部節點的最短路徑的長度。你能夠在任一節點開始和中止，也能夠屢次重訪節點，而且能夠重用邊。

示例 1：

輸入：[[1,2,3],[0],[0],[0]]
輸出：4
解釋：一個可能的路徑爲 [1,0,2,0,3]

示例 2：

輸入：[[1],[0,2,4],[1,3,4],[2],[1,2]]
輸出：4
解釋：一個可能的路徑爲 [0,1,4,2,3]

提示：

1. 1 <= graph.length <= 12
2. 0 <= graph[i].length < graph.length

---

Runtime: 240 ms

Memory Usage: 19.5 MB

 1 class Solution {
 2     func shortestPathLength(_ graph: [[Int]]) -> Int {
 3         var n:Int = graph.count
 4         var fullMask:Int = (1 << n) - 1
 5         var visited:Set<String> = Set<String>()
 6         var que:[Node] = [Node]()
 7         for i in 0..<n
 8         {
 9             var node:Node = Node(i, 1<<i)
10             que.append(node)
11             visited.insert(node.toString())
12         }
13         var level:Int = 0
14         while(!que.isEmpty)
15         {
16             var size:Int = que.count
17             for i in 0..<size
18             {
19                 var node = que.removeFirst()
20                 if node.mask == fullMask {return level}
21                 for next in graph[node.id]
22                 {
23                     var nextNode:Node = Node(next, node.mask | (1 << next))
24                     if visited.contains(nextNode.toString()) {continue}
25                     que.append(nextNode)
26                     visited.insert(nextNode.toString())
27                 }
28             }
29             level += 1
30         }
31         return level
32     }
33 }
34 
35 class Node {
36     var id:Int = 0
37     var mask:Int = 0
38     
39     init(_ id:Int,_ mask:Int)
40     {
41         self.id = id
42         self.mask = mask        
43     }
44     
45     func toString() -> String
46     {
47         return String(id) + " " + String(mask)
48     }
49 }