Total Accepted: 53879 Total Submissions: 190701 Difficulty: Medium
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* pivot = NULL;
ListNode* cur = head;
ListNode* insert_pos = cur;
ListNode* insert_pos_pre = NULL;
while(cur && cur->val < x){
insert_pos_pre = cur;
cur = cur->next;
insert_pos = cur;
}
pivot = cur; /*
pivot 左边做插入，insert_node_pre,inser_node
pivot 右边做删除, delete_node_pre,delete_node
*/ ListNode* possible_delete_node_pre = pivot;
ListNode* possible_delete_node = pivot ? pivot->next : NULL; while(possible_delete_node){
ListNode* possible_delete_node_next = possible_delete_node->next;
if(possible_delete_node->val < x){
if(insert_pos_pre){
insert_pos_pre->next = possible_delete_node ;
}else{
head = possible_delete_node;
}
possible_delete_node->next = insert_pos; insert_pos_pre = possible_delete_node;
insert_pos = insert_pos_pre->next; possible_delete_node_pre ->next = possible_delete_node_next; }else{
possible_delete_node_pre = possible_delete_node;
}
possible_delete_node = possible_delete_node_next;
} return head; }
};