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【Lintcode】105.Copy List with Random Pointer

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題目:

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.

題解:

Solution 1 ()

class Solution {
public:
    RandomListNode *copyRandomList(RandomListNode *head) {
        if (head == nullptr) return
nullptr; RandomListNode* dummy = new RandomListNode(-1); RandomListNode* cur = head; RandomListNode* node = dummy; unordered_map<RandomListNode*, RandomListNode*> map; while (cur) { RandomListNode* tmp = new RandomListNode(cur->label); node
->next = tmp; map[cur] = node->next; node = node->next; cur = cur->next; } node = dummy->next; cur = head; while (node) { node->random = map[cur->random]; node = node->next; cur
= cur->next; } return dummy->next; } };

Solution 2 ()

class Solution {
public:
    RandomListNode *copyRandomList(RandomListNode *head) {
        if (!head) return head;
        RandomListNode* cur = head;
        while (cur) {
            RandomListNode* node = new RandomListNode(cur->label);
            node->next = cur->next;
            cur->next = node;
            cur = node->next;
        }
        cur = head;
        while (cur) {
            if (cur->random) {
                cur->next->random = cur->random->next;
            }
            cur = cur->next->next;
        }
        cur = head;
        RandomListNode* first = cur->next;
        while (cur) {
            RandomListNode* tmp = cur->next;
            cur->next = tmp->next;
            if (tmp->next) {
                tmp->next = tmp->next->next;
            }
            cur = cur->next;  
        }
        
        return first;
    }
};

Solution 3 ()

class Solution {
public:
    RandomListNode *copyRandomList(RandomListNode *head) {
        RandomListNode *newHead, *l1, *l2;
        if (head == NULL) return NULL;

        for (l1 = head; l1 != NULL; l1 = l1->next) {
            l2 = new RandomListNode(l1->label);
            l2->next = l1->random;
            l1->random = l2;
        }
        
        newHead = head->random;
        for (l1 = head; l1 != NULL; l1 = l1->next) {
            l2 = l1->random;
            l2->random = l2->next ? l2->next->random : NULL;
        }
        
        for (l1 = head; l1 != NULL; l1 = l1->next) {
            l2 = l1->random;
            l1->random = l2->next;
            l2->next = l1->next ? l1->next->random : NULL;
        }

        return newHead;
    }
};

【Lintcode】105.Copy List with Random Pointer