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Partition List.cpp
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Partition List.cpp
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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) {
if (head == NULL) return head;
ListNode *cur = head, *pBigTail = NULL, *pBigHead = NULL;
ListNode *pSmallTail = NULL, *pSmallHead = NULL;
while (cur != NULL) {
if (cur->val >= x) {
if (pBigHead == NULL) {
pBigHead = pBigTail = cur;
} else {
pBigTail->next = cur;
pBigTail = cur;
}
} else {
if (pSmallHead == NULL) {
pSmallHead = pSmallTail = cur;
} else {
pSmallTail->next = cur;
pSmallTail = cur;
}
}
cur = cur->next;
}
if (pBigTail) pBigTail->next = NULL;
if (pSmallHead == NULL) return pBigHead;
else {
pSmallTail->next = pBigHead;
return pSmallHead;
}
}
};