To prove safety offer - replication complex list

Title Description

A complex input list (each node has a node value, and two pointers, one pointing to the next node, a special pointer to any other node), returns a value after the head of the list replication complex. (Note that the output results do not return parameter node reference, otherwise the program will return empty sentenced questions directly)

Violence to solve:

First traverse from beginning to end, a new random pointer for the empty list. We were all kept in order with the two nodes in two lists list.

Then traverse from beginning to end, according to a random position in the original list of list, the linked list to the new random reference imparting respective nodes.

class Solution:
    # 返回 RandomListNode
    def Clone(self, pHead):
        if not pHead:
            return None
        node = RandomListNode(pHead.label)
        head = node
        pHead_s = pHead
        nodes = [pHead]
        nodes_copy = [node]
        pHead = pHead.next
        
        while pHead:
            node.next = RandomListNode(pHead.label)
            node = node.next
            nodes.append(pHead)
            nodes_copy.append(node)
            pHead = pHead.next
        head_s = head
        while pHead_s:
            if pHead_s.random:
                head_s.random = nodes_copy[nodes.index(pHead_s.random)]
            pHead_s = pHead_s.next
            head_s = head_s.next
        return head

optimization:

The time complexity of the above-violence is O (n ^ 2), the spatial complexity is O (n)

Read an answer on the cattle off, time complexity is O (n), space complexity is O (1)

class Solution:
    def Clone(self, pHead):
        pHead_s = pHead
        while pHead_s:
            temp = pHead_s.next
            pHead_s.next = RandomListNode(pHead_s.label)
            pHead_s.next.next = temp
            pHead_s = pHead_s.next.next
        
        pHead_s = pHead
        while pHead_s:
            if pHead_s.random:
                pHead_s.next.random = pHead_s.random.next
            pHead_s = pHead_s.next.next
        
        pHead_s = pHead
        head_s = pHead_s.next
        head = head_s
        while head_s.next:
            pHead_s.next = pHead_s.next.next
            head_s.next = head_s.next.next
            pHead_s = pHead_s.next
            head_s = head_s.next
        return head