86

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* partition(ListNode* head, int x) {
        ListNode *dummy = new ListNode(0, head);
        ListNode *partition = new ListNode(0);
        ListNode *curr = dummy, *pcurr = partition;
        while(curr->next){
            if(curr->next->val < x){
                pcurr->next = curr->next;
                pcurr = pcurr->next;
                curr->next = curr->next->next;
            }
            else{
                curr = curr->next;
            }
        }
        pcurr->next = dummy->next;
        return partition->next;
    }
};