题解 | #链表分割#

/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};*/
#include <cstddef>
class Partition {
public:
    ListNode* partition(ListNode* pHead, int x) {
    struct ListNode* gGuard,*gTail,*lGuard,*lTail;
    struct ListNode*cur = pHead;
    gGuard = gTail = (struct ListNode*)malloc(sizeof(struct ListNode));
    lGuard = lTail = (struct ListNode*)malloc(sizeof(struct ListNode));
    gTail->next = lTail->next = NULL;

    while (cur)
    {
        if (cur->val < x)
        {
            lTail->next = cur ;
            lTail = lTail->next; 
        }
        else 
        {
            gTail->next = cur ;
            gTail = gTail->next;
        }
        cur = cur->next;
    }

    lTail->next = gGuard->next;
    gTail->next = NULL;
    pHead = lGuard->next;
    free(lGuard);
    free(gGuard);
    return pHead;
    }
};