LeetCode 86. Partition List

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.

For example,
Given 1->4->3->2->5->2 and x = 3,
return 1->2->2->4->3->5.

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/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode* partition(ListNode *head, int x) {        ListNode smaller_head(0);        ListNode larger_head(0);        ListNode *smaller_tail = &smaller_head;        ListNode *larger_tail = &larger_head;        while (head != NULL) {            if (head->val < x) {                smaller_tail->next = head;                smaller_tail = head;            }            else {                larger_tail->next = head;                larger_tail = head;            }            head = head->next;        }        smaller_tail->next = larger_head.next;        larger_tail->next = NULL;        return smaller_head.next;    }};