題目描述
給定一個鏈表和一個特定值 x,對鏈表進行分隔,使得所有小於 x 的節點都在大於或等於 x 的節點之前。
你應當保留兩個分區中每個節點的初始相對位置。
示例:
輸入: head = 1->4->3->2->5->2, x = 3
輸出: 1->2->2->4->3->5
我的思路
藉助兩個輔助鏈表實現即可,然後合併兩個鏈表。代碼如下:
/**
* 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) {
if(head == NULL) return head;
ListNode* first = new ListNode(0);
ListNode* last = new ListNode(0);
ListNode* cur = first;
ListNode* cur2 = last;
while(head != NULL){
if(head->val < x){
first->next = new ListNode(0);
first->next->val = head->val;
first = first->next;
}
else if(head->val >= x){
last->next = new ListNode(0);
last->next->val = head->val;
last = last->next;
}
head = head->next;
}
if(first != NULL)first->next = cur2->next;
return cur->next;
}
};