[LeetCode] 132: Copy List with Random Pointer

[Problem]

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.

[Solution]

/**
 * Definition for singly-linked list with a random pointer.
 * struct RandomListNode {
 *     int label;
 *     RandomListNode *next, *random;
 *     RandomListNode(int x) : label(x), next(NULL), random(NULL) {}
 * };
 */
class Solution {
public:
RandomListNode *copyRandomList(RandomListNode *head) {
// Note: The Solution object is instantiated only once and is reused by each test case.
// null node
if(NULL == head) return head;

// create new nodes of the old list
map<RandomListNode *, int> myMap;// stores the index of the nodes in the old list
vector<RandomListNode *> newNodes;// new nodes
RandomListNode *p = head;
int i = 0, j = 0;
while(p != NULL){
RandomListNode *node = new RandomListNode(p->label);
newNodes.push_back(node);

// stores index and increase index
myMap[p] = i++;
p = p->next;
}

// copy
p = head;
i = 0;
while(p != NULL){
if(p->next != NULL){
newNodes[i]->next = newNodes[i+1];
}
if(p->random != NULL){
newNodes[i]->random = newNodes[myMap[p->random]];
}
i++;
p = p->next;
}
return newNodes[0];
}
};

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