solve

Author: sonjh1217

clone-graph/sonjh1217.swift

@@ -0,0 +1,39 @@
+/**
+ * Definition for a Node.
+ * public class Node {
+ *     public var val: Int
+ *     public var neighbors: [Node?]
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.neighbors = []
+ *     }
+ * }
+ */
+
+class Solution {
+    // O(V+E) time / O(V) space
+    func cloneGraph(_ node: Node?) -> Node? {
+        guard let node = node else {
+            return nil
+        }
+        var newNodeByVal = [Int: Node]()
+        return copy(node: node, newNodeByVal: &newNodeByVal)
+    }
+    
+    func copy(node: Node, newNodeByVal: inout [Int: Node]) -> Node {
+        if let node = newNodeByVal[node.val] {
+            return node
+        }
+        var newNode = Node(node.val)
+        newNodeByVal[node.val] = newNode
+        
+        for neighbor in node.neighbors {
+            guard let neighbor = neighbor else {
+                continue
+            }
+            let newNeighbor = copy(node: neighbor, newNodeByVal: &newNodeByVal)
+            newNode.neighbors.append(newNeighbor)
+        }
+        return newNode
+    }
+}