首先，演示一个错误的reverList

1 class Solution { 2     public: 3         ListNode* reverse(ListNode* root) 4         { 5             if(NULL == root) 6                 return NULL; 7             ListNode* pCur = root; 8             ListNode* pNext = root->next; 9 10             while(pNext)11             {12                 pNext = pNext->next;13                 pCur->next->next = pCur;14                 pCur = pCur->next;15             }16             root->next = NULL;17             return pCur;18         }19 20 };

(2)--------->(3)-------->(4)----------->(5)--------->NULL

首先pCur指向2,pNext指向3；

pNext=pNext->next; pNext指向4，

pCur->next->next = pCur，然后3--->4 的指针断了， 从此pCur就自己转圈了。。。

正确的reverseList

ListNode * reverseList(ListNode* head){    if(head == NULL) return NULL;    ListNode *pre = NULL;    ListNode *cur = head;    ListNode *next = NULL;    while(cur)    {        next = cur->next;        cur->next = pre;        pre = cur;        cur = next;    }    return pre;}

 

 

 

 

这个题目也不难，注意dummy节点的使用，另外，记得最后carrybit的处理

/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:        ListNode *addTwoNumbers(ListNode *l1, ListNode *l2)        {            if(l1 == NULL)                return l2;            if(l2 == NULL)                return l1;            ListNode* p1 = l1;            ListNode* p2 = l2;            ListNode dummy(-1);            ListNode* pNew = &dummy;            int carry = 0;            int sum = 0;            while(p1 && p2)            {                sum = (p1->val + p2->val + carry)%10;                carry= (p1->val + p2->val + carry)/10;                pNew->next = new ListNode(sum);                pNew = pNew->next;                p1 = p1->next;                p2 = p2->next;            }            while(p1)            {                sum = (p1->val +  carry)%10;                carry= (p1->val + carry)/10;                pNew->next = new ListNode(sum);                pNew = pNew->next;                p1 = p1->next;            }            while(p2)            {                sum = (p2->val +  carry)%10;                carry= (p2->val + carry)/10;                pNew->next = new ListNode(sum);                pNew = pNew->next;                p2 = p2->next;            }            if(carry)            {                pNew->next = new ListNode(carry);                pNew = pNew->next;            }                         return dummy.next;        }              };