[notes for question brushing] delete continuous nodes with a total value of zero from the linked list

subject ：

Give you a list of the head node  head, Please write code , Delete from the linked list repeatedly The sum of the   The value is 0 A sequence of continuous nodes , Until there is no such sequence .

After deleting , Please return the head node of the final result linked list .

You can return any answer that meets the requirements of the question .

（ Be careful , All sequences in the following example , All right.  ListNode  Representation of object serialization .）

Example 1：

Input ：head = [1,2,-3,3,1]
Output ：[3,1]
Tips ： answer [1,2,1] It's also true .
Example 2：

Input ：head = [1,2,3,-3,4]
Output ：[1,2,4]
Example 3：

Input ：head = [1,2,3,-3,-2]
Output ：[1]
 

Tips ：

The list given to you may have 1 To  1000  Nodes .
For each node in the linked list , The value of the node ：-1000 <= node.val <= 1000.

source ： Power button （LeetCode）
link ：https://leetcode.cn/problems/remove-zero-sum-consecutive-nodes-from-linked-list

answer ：

        This question uses c The key to language is to grasp the two cycles .

        Because it records the sum of consecutive , Then this interval can be （ Subscript is the benchmark , From 0 Start ）0~1 0~2... 1~2..2~3... This also shows that we need to start from each node of the linked list as the head and look back . Then, naturally, an accumulated variable can be defined later , And also define a pointer that is easy to cycle later , When the sum is 0 It means that this interval adds up to 0, You can give up . Then the head of this interval is the previous next You can point to the end of this interval next 了 , This completes a rounding off of the interval .

        In order to avoid the situation that the head node needs to be rounded off , So we need to create a node by ourselves , then next Point to the head node . The code is as follows ：

struct ListNode* removeZeroSumSublists(struct ListNode* head){
    // Create a head node , Prevent the header node from being deleted 
    struct ListNode* s = (struct ListNode*)malloc(sizeof(struct ListNode));
    s->next = head;
    struct ListNode* front = s;
    int x = 0;
    while(front)
    {
        struct ListNode* res = front->next;
        while(res)
        {
            x += res->val;
            if (x == 0)
            {
                front->next = res->next;
            }
            res = res->next;
        }
        x = 0;
        front = front->next;
    }
    return s->next;
}