Leetcode: Copy List with Random Pointer

Copy List with Random Pointer.cpp

/**
 * 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) {}
 * };
 */
typedef RandomListNode Node;
class Solution {
public:
    void insertShallow(Node * n) {
        while (n) {
            Node * p = n;  n = n->next;
            Node * next = p->next;
            Node * sha = new Node(*p);
            p->next = sha;
            sha->next = next;
        }
    }
    void ajustShallow(Node * n) {
        while (n) {
            Node * p = n->next;  n = n->next->next;
            if (p->random) p->random = p->random->next;
        }
    }
    Node * pickList(Node * n) {
        Node * head = n->next;
        while (n) {
            Node * p = n;  n = n->next->next;
            Node * copy = p->next;
            p->next = n;
            if (n) copy->next = n->next;
            else copy->next = NULL;
        }
        return head;
    }
    RandomListNode *copyRandomList(RandomListNode *head) {
        if (!head) return NULL;
        insertShallow(head);
        ajustShallow(head);
        return pickList(head);
    }
};

Runtime error了一次才AC的
太不上心了，教训值得铭记！
写完一定要做Check
每一个"->"前面的东西你一定要保证它非空

p->random = p->random->next;
这句我忘记加guard了

if (p->random) p->random = p->random->next;

之前是这里没有加判断所以 Runtime Error 了吗？

其它 :lgtm:

是的, 就是忘记判断p->random是否为空了

但是这个错误终究还是整个coding的过程不严谨导致的