链表篇

/*
// Definition for a Node.
class Node {
    int val;
    Node next;
    Node random;

    public Node(int val) {
        this.val = val;
        this.next = null;
        this.random = null;
    }
}
*/

class Solution {
    public Node copyRandomList(Node head) {
        if(head==null){
            return null;
        }
        java.util.Map<Node,Node>dict=new java.util.HashMap<>();
        Node cur=head;
        //复制各节点，建立"key-value"的map映射
        while (cur!=null){
            dict.put(cur,new Node(cur.val));
            cur=cur.next;
        }
        cur=head;
        //构建next和random指向
        while(cur!=null){
            dict.get(cur).next=dict.get(cur.next);
            dict.get(cur).random=dict.get(cur.random);
            cur=cur.next;
        }
        //返回新链表的头结点
        return dict.get(head);   
    }
}