feat: add solutions to lc/lcof problem: Copy List with Random Pointer

Author: yanglbme

lcof/面试题35. 复杂链表的复制/README.md

@@ -51,6 +51,22 @@
 
 <!-- 这里可写通用的实现逻辑 -->
 
+首先，遍历链表，完成对每个旧节点的复制。
+
+```bash
+A -> B -> C -> D -> null
+
+=>
+
+A -> A1 -> B -> B1 -> C -> C1 -> D -> D1 -> null
+```
+
+接着设置新节点的 ramdom 指针。
+
+然后遍历链表，修改旧节点和新节点的指向，将旧节点指向下一个旧节点，而新节点指向下一个新节点。
+
+最后返回第一个新节点即可。
+
 <!-- tabs:start -->
 
 ### **Python3**
@@ -66,23 +82,31 @@ class Node:
         self.next = next
         self.random = random
 """
+
 class Solution:
     def copyRandomList(self, head: 'Node') -> 'Node':
-        if not head:
+        if head is None:
             return None
-        copy_head = Node(-1)
-        cur, t = copy_head, head
-        cache = {}
-        while t:
-            cur.next = Node(t.val)
-            cache[t] = cur.next
-            cur, t = cur.next, t.next
-        t, cur = head, copy_head.next
-        while t:
-            cur.random = cache.get(t.random)
-            cur, t = cur.next, t.next
-        return copy_head.next
 
+        cur = head
+        while cur:
+            node = Node(cur.val, cur.next)
+            cur.next = node
+            cur = node.next
+        
+        cur = head
+        while cur:
+            cur.next.random = None if cur.random is None else cur.random.next
+            cur = cur.next.next
+        
+        copy = head.next
+        cur = head
+        while cur:
+            next = cur.next
+            cur.next = next.next
+            next.next = None if next.next is None else next.next.next
+            cur = cur.next
+        return copy
 ```
 
 ### **Java**
@@ -104,29 +128,139 @@ class Node {
     }
 }
 */
+
 class Solution {
     public Node copyRandomList(Node head) {
         if (head == null) {
             return null;
         }
-        Map<Node, Node> map = new HashMap<>();
-        Node copyHead = new Node(-1);
-        Node cur = copyHead, t = head;
-        while (t != null) {
-            Node node = new Node(t.val);
-            map.put(t, node);
+
+        Node cur = head;
+        while (cur != null) {
+            Node node = new Node(cur.val);
+            node.next = cur.next;
             cur.next = node;
-            cur = node;
-            t = t.next;
+            cur = node.next;
         }
-        cur = copyHead.next;
-        while (head != null) {
-            cur.random = map.get(head.random);
+
+        cur = head;
+        while (cur != null) {
+            cur.next.random = cur.random == null ? null : cur.random.next;
+            cur = cur.next.next;
+        }
+
+        Node copy = head.next;
+        cur = head;
+        while (cur != null) {
+            Node next = cur.next;
+            cur.next = next.next;
+            next.next = next.next == null ? null : next.next.next;
             cur = cur.next;
-            head = head.next;
         }
-        return copyHead.next;
+        return copy;
+    }
+}
+```
+
+### **C++**
+
+```cpp
+/*
+// Definition for a Node.
+class Node {
+public:
+    int val;
+    Node* next;
+    Node* random;
+    
+    Node(int _val) {
+        val = _val;
+        next = NULL;
+        random = NULL;
+    }
+};
+*/
+
+class Solution {
+public:
+    Node* copyRandomList(Node* head) {
+        if (!head) {
+            return nullptr;
+        }
+        Node* cur = head;
+        while (cur) {
+            Node* node = new Node(cur->val);
+            node->next = cur->next;
+            cur->next = node;
+            cur = node->next;
+        }
+
+        cur = head;
+        while (cur) {
+            cur->next->random = cur->random ? cur->random->next : nullptr;
+            cur = cur->next->next;
+        }
+
+        Node* copy = head->next;
+        cur = head;
+        while (cur) {
+            Node* next = cur->next;
+            cur->next = next->next;
+            next->next = next->next ? next->next->next : nullptr;
+            cur = cur->next;
+        }
+        return copy;
+    }
+};
+```
+
+### **C#**
+
+```cs
+/*
+// Definition for a Node.
+public class Node {
+    public int val;
+    public Node next;
+    public Node random;
+    
+    public Node(int _val) {
+        val = _val;
+        next = null;
+        random = null;
+    }
+}
+*/
+
+public class Solution {
+    public Node CopyRandomList(Node head) {
+        if (head == null) {
+            return null;
+        }
+        
+        Node cur = head;
+        while (cur != null) {
+            Node node = new Node(cur.val);
+            node.next = cur.next;
+            cur.next = node;
+            cur = node.next;
+        }
 
+        cur = head;
+        while (cur != null) {
+            cur.next.random = cur.random == null ? null : cur.random.next;
+            cur = cur.next.next;
+        }
+
+        Node copy = head.next;
+        cur = head;
+        while (cur != null) {
+            Node next = cur.next;
+            cur.next = next.next;
+            next.next = next.next == null ? null : next.next.next;
+            cur = cur.next;
+        }
+        return copy;
     }
 }
 ```
@@ -142,96 +276,94 @@ class Solution {
  *    this.random = random;
  * };
  */
+
 /**
  * @param {Node} head
  * @return {Node}
  */
-var copyRandomList = function (head) {
-  function copy(node) {
-    if (!node) return null;
-    if (isRead.get(node)) return isRead.get(node);
-    let newNode = new Node(node.val);
-    isRead.set(node, newNode);
-    newNode.random = copy(node.random);
-    newNode.next = copy(node.next);
-    return newNode;
-  }
-  let isRead = new Map();
-  return copy(head);
+var copyRandomList = function(head) {
+    if (head == null) {
+        return null;
+    }
+    let cur = head;
+    while (cur != null) {
+        let node = new Node(cur.val, cur.next);
+        cur.next = node;
+        cur = node.next;
+    }
+
+    cur = head;
+    while (cur != null) {
+        cur.next.random = cur.random == null ? null : cur.random.next;
+        cur = cur.next.next;
+    }
+
+    let copy = head.next;
+    cur = head;
+    while (cur != null) {
+        let next = cur.next;
+        cur.next = next.next;
+        next.next = next.next == null ? null : next.next.next;
+        cur = cur.next;
+    }
+    return copy;
 };
 ```
 
 ### **Go**
 
 ```go
+/**
+ * Definition for a Node.
+ * type Node struct {
+ *     Val int
+ *     Next *Node
+ *     Random *Node
+ * }
+ */
+
 func copyRandomList(head *Node) *Node {
     if head == nil {
         return nil
     }
-    cur, next := head,head
-    //完成对当前节点的复制
+
+    cur := head
     for cur != nil {
-        next = cur.Next
-        cur.Next = &Node{
+        node := &Node{
             Val: cur.Val,
-            Next: next,
+            Next: cur.Next,
             Random: nil,
         }
-        cur = next
+        cur.Next = node
+        cur = node.Next
     }
-    //设置复制节点的random节点
+
     cur = head
-    curCopy := head
     for cur != nil {
-        next = cur.Next.Next
-        curCopy = cur.Next
         if cur.Random == nil {
-            curCopy.Random = nil
+            cur.Next.Random = nil
         } else {
-            curCopy.Random = cur.Random.Next
+            cur.Next.Random = cur.Random.Next
         }
-        cur = next
+        cur = cur.Next.Next
     }
-    res := head.Next
+
+    copy := head.Next
     cur = head
     for cur != nil {
-        next = cur.Next.Next
-        curCopy = cur.Next
-        cur.Next = next
-        if next != nil {
-            curCopy.Next = next.Next
+        next := cur.Next
+        cur.Next = next.Next
+        if (next.Next == nil) {
+            next.Next = nil
         } else {
-            curCopy.Next = nil
+            next.Next = next.Next.Next
         }
         cur = cur.Next
     }
-    return res
+    return copy
 }
 ```
 
-### **C++**
-
-```cpp
-class Solution {
-public:
-    Node* copyRandomList(Node* head) {
-        unordered_map<Node*, Node*> m;
-        Node* p = head;
-        while (p) {
-            m[p] = new Node(p->val);
-            p = p->next;
-        }
-        p = head;
-        while (p) {
-            m[p]->next = m[p->next];
-            m[p]->random = m[p->random];
-            p = p->next;
-        }
-        return m[head];
-    }
-};
-```
-
 ### **...**
 
 ```