Partition List

Desicription

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.

Solution

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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* low = new ListNode(0);
ListNode* high = new ListNode(0);
ListNode* base_low = low;
ListNode* base_high = high;
while(head){
if(head->val < x)
low->next = head, low = low->next;
else
high->next = head, high = high->next;
head = head->next;
}
high->next = NULL;
low->next = base_high->next;
return base_low->next;
}
};