LeetCode問題解(88):Copy List with Random Pointer

タイトル:
A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.
Return a deep copy of the list. 問題:
2つの方法:O(1)space in place copy、HashTable追加O(n)space copy.
C++作り方一:

class Solution {
public:
    RandomListNode *copyRandomList(RandomListNode *head) {
        if(!head)
            return NULL;
        RandomListNode *p = head;
        while(p != NULL) {
            RandomListNode *newNode = new RandomListNode(p->label);
            newNode->next = p->next;
            p->next = newNode;
            p = p->next->next;
        }
        
        p = head;
        while(p != NULL) {
            if(p->random != NULL)
                p->next->random = p->random->next;
            p = p->next->next;
        }
        
        RandomListNode *newHead = head->next;
        p = head;
        RandomListNode *q = head->next;
        
        while(p != NULL) {
            p->next = q->next;
            if(q->next != NULL)
                q->next = q->next->next;
            p = p->next;
            if(p != NULL)
                q = p->next;
        }

        return newHead;
        
    }
};

C++作り方2:

class Solution {
public:
    RandomListNode *copyRandomList(RandomListNode *head) {
        if(!head)
            return NULL;
        unordered_map<RandomListNode*, RandomListNode*> nodeToNode;
        RandomListNode *p = head;
        RandomListNode *newListHead = copyNode(p, nodeToNode);
        RandomListNode *q = newListHead;
        while(q) {
            if(head->random != NULL)
                q->random = nodeToNode[head->random];
            q = q->next;
            head = head->next;
        }
        return newListHead;
    }
    
    RandomListNode* copyNode(RandomListNode* head, unordered_map<RandomListNode*, RandomListNode*> & nodeToNode) {
        if(!head)
            return NULL;
        RandomListNode* newHead = new RandomListNode(head->label);
        nodeToNode.insert(pair<RandomListNode*, RandomListNode*>(head, newHead));
        newHead->next = copyNode(head->next, nodeToNode);
        return newHead;
    }
};

Javaの作り方1:

/**
 * Definition for singly-linked list with a random pointer.
 * class RandomListNode {
 *     int label;
 *     RandomListNode next, random;
 *     RandomListNode(int x) { this.label = x; }
 * };
 */
public class Solution {
    public RandomListNode copyRandomList(RandomListNode head) {
        if(head == null)
            return null;
        
        RandomListNode p = head;
        while(p != null) {
            RandomListNode newNode = new RandomListNode(p.label);
            newNode.next = p.next;
            p.next = newNode;
            p = p.next.next;
        }
        
        p = head;
        while(p != null) {
            if(p.random != null)
                p.next.random = p.random.next;
            p = p.next.next;
        }
        
        p = head;
        RandomListNode newHead = p.next;
        while(p != null) {
            RandomListNode temp = p.next;
            p.next = temp.next;
            if(p.next != null)
                temp.next = p.next.next;
            p = p.next;
        }
        
        return newHead;
    }
}

Pythonの作り方2:

# Definition for singly-linked list with a random pointer.
# class RandomListNode:
#     def __init__(self, x):
#         self.label = x
#         self.next = None
#         self.random = None

class Solution:
    # @param head, a RandomListNode
    # @return a RandomListNode
    def copyRandomList(self, head):
        if head == None:
            return None
        d = {}
        p = head
        newHead = self.copyList(p, d)
        p = head
        q = newHead
        while p != None:
            if p.random != None:
                q.random = d[p.random]
            p = p.next
            q = q.next
        return newHead
        
    def copyList(self, head, d):
        if head == None:
            return head
        
        newNode = RandomListNode(head.label)
        d[head] = newNode
        newNode.next = self.copyList(head.next, d)
        return newNode