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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.

/** * 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* leftHead = new ListNode(-1);        ListNode* rightHead = new ListNode(-1);        ListNode* p1 = leftHead;        ListNode* p2 = rightHead;        ListNode* p = head;        while(p){            if(p->val<x){                p1->next = p;                p1 = p;                p = p->next;            }else{                p2->next = p;                p2 = p;                p = p->next;            }        }        p1->next = rightHead->next;        p2->next = nullptr;        return leftHead->next;    }};

 

Partition List