133. Clone Graph 138. Copy List with Random Pointer 拷贝图和链表

133. Clone Graph

Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.

OJ‘s undirected graph serialization:

Nodes are labeled uniquely.

We use # as a separator for each node, and , as a separator for node label and each neighbor of the node.

As an example, consider the serialized graph {0,1,2#1,2#2,2}.

The graph has a total of three nodes, and therefore contains three parts as separated by #.

1. First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
2. Second node is labeled as 1. Connect node 1 to node 2.
3. Third node is labeled as 2. Connect node 2 to node 2 (itself), thus forming a self-cycle.

Visually, the graph looks like the following:

       1
      /      /       0 --- 2
         /          \_/

class Solution {
public:
    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
        if(node == NULL)
            return NULL;
        UndirectedGraphNode *cloneNode = new UndirectedGraphNode(node->label);
        map<UndirectedGraphNode*, UndirectedGraphNode*> m;
        m[node] = cloneNode;
        queue<UndirectedGraphNode*> q;
        q.push(node);
        while(!q.empty())
        {
            UndirectedGraphNode *t = q.front();
            q.pop();
            for(int i = 0; i < t->neighbors.size(); i++)
            {
                UndirectedGraphNode *neighbor = t->neighbors[i];
                if(m.find(neighbor) == m.end())
                {
                    UndirectedGraphNode *p = new UndirectedGraphNode(neighbor->label);
                    m[neighbor] = p;
                    m[t]->neighbors.push_back(p);
                    q.push(neighbor);
                }
                else
                {
                    m[t]->neighbors.push_back(m[neighbor]);
                }
            }
        }
        return cloneNode;
    }
};

138. Copy List with Random Pointer

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.

/**
 * 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) {}
 * };
 */

（1）

* Consider we have a linked list as below:
*
* node1->random = node2;
* node2->random = node1;
* node3->random = node1;
*
* +-------------+
* | v
* +-------+ +-------+ +-------+
* | node1 |----> node2 |----> node3 |--->NULL
* +-------+ +-------+ +-------+
* ^ ^ | |
* | +-----------+ |
* +--------------------------+
*
*
* To copy the list,
*
* 1) We insert a new node for each node‘s next position
*
*
* +-------------------------+
* | v
* +--+----+ +-----+ +-------+ +-----+ +-------+ +-----+
* | node1 |---> | NEW |----> node2 |---> | NEW |----> node3 |---> | NEW | ---> NULL
* +-------+ +-----+ +---+---+ +-----+ +--+----+ +-----+
* ^ ^ | |
* | +-----------------------+ |
* +--------------------------------------------------+
*
* 2) Then, we can construt the new node‘s random pointer:
*
* (node1->next) -> random = (node1->random) -> next;
*
* 3) After we take out all of the "NEW" node to finish the copy.

class Solution {
public:
    RandomListNode *copyRandomList(RandomListNode *head) {
        RandomListNode *p = NULL, *h=NULL, *t=NULL;
        if (head == NULL){
            return NULL;
        }

        //creat a new node for each node and insert its next
        p = head;
        while ( p != NULL){
            RandomListNode *node = new RandomListNode(p->label);
            node->next = p->next;
            p->next = node;
            p = node->next;
        }

        //copy random pointer for each new node
        p = head;
        while (p != NULL){
            if (p->random != NULL){
                p->next->random = p->random->next;
            }
            p = p->next->next;
        }

        //break to two list
        p = head;
        h = t = head->next;
        while ( p != NULL ){
            p->next = p->next->next;
            if (t->next!=NULL){
                t->next = t->next->next;
            }

            p = p->next;
            t = t->next;
        }

        return h;
    }
};

（2）

* Considering we have a link as below:
*
*
* +-------------+
* | v
* +-------+ +-------+ +-------+
* | node1 |----> node2 |----> node3 |--->NULL
* +-------+ +-------+ +-------+
* ^ ^ | |
* | +-----------+ |
* +--------------------------+
*
* 1) Using a map to store each node‘s random pointer‘s position
*
* map[node1->random] = 1;
* map[node2->random] = 0;
* map[node3->random] = 0;
*
* 2) Clone the linked list (only consider the next pointer)
*
* new1 --> new2 --> new3 --> NULL
*
* 3) Using an array to strore the order of the cloned linked-list
*
* v[0] = &new1
* v[1] = &new2
* v[2] = &new3
*
* 4) Then we can clone the random pointers.
*
* new->random = v [ map[node->random] ]

class MySolution {
public:
    RandomListNode *copyRandomList(RandomListNode *head) {

        RandomListNode *p = NULL, *h=NULL, *t=NULL;
        //using a map to store the random pointer‘s postion.
        map<RandomListNode*, int> m;
        //construct the map
        int pos =0;
        for ( p = head; p != NULL; p = p->next, pos++){
            m[p] = pos;
        }

        //clone the linked list  (only consider the next pointer)
        //and using a vector to store each node‘s postion.
        vector<RandomListNode*> v;
        for (p = head; p != NULL; p = p->next){
            RandomListNode *node = new RandomListNode(p->label);
            v.push_back(node);
            if (h==NULL){
                h = t = node;
            }else{
                t->next = node;
                t = node;
            }
        }

        //p => source link head
        //t => new link head
        //move the p and t synchronously, and
        //     t->random = vector[ map[p->random] ];
        for (t=h, p = head; t!=NULL && p!= NULL; p=p->next, t=t->next){
            if (p->random!=NULL) {
                pos = m[p->random];
                t->random = v[pos];
            }
        }

        return h;

    }
};