[leetcode]-86. Partition List（C语言）

Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.

You should preserve the original relative order of the nodes in each of the two partitions.

Example:

Input: head = 1->4->3->2->5->2, x = 3
Output: 1->2->2->4->3->5

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* partition(struct ListNode* head, int x) {
    if(head==NULL||head->next==NULL)
        return head;
    int flag=0;
    struct ListNode *cur,*pre,*p,*q,*hhead;
    pre=(struct ListNode *)malloc(sizeof(struct ListNode));
    hhead=(struct ListNode *)malloc(sizeof(struct ListNode));
    if(head->valnext=head;
        flag=1;
    }
    pre->next=head;
    cur=head;
    while(cur!=NULL)
    {
        if(cur->val>=x)
            break;
        cur=cur->next;
        pre=pre->next;
    }
    if(cur==NULL)
        return head;
    q=cur;
    cur=cur->next;
    while(cur!=NULL)
    {
        if(cur->valnext=cur;
                flag=1;
            }
            p=cur->next;
            cur->next=pre->next;
            pre->next=cur;
            q->next=p;
            pre=pre->next;
            cur=p;
            continue;
        }
        q=q->next;
        cur=cur->next;
    }
    if(flag==0)
        hhead->next=head;
    return hhead->next;
}