单链表算法 - 链表分割

链表分割_牛客题霸_牛客网现有一链表的头指针 ListNode* pHead，给一定值x，编写一段代码将所有小于x的。题目来自【牛客题霸】https://www.nowcoder.com/practice/0e27e0b064de4eacac178676ef9c9d70思路:

代码:

/* struct ListNode {     int val;     struct ListNode *next;     ListNode(int x) : val(x), next(NULL) {} };*/ class Partition { public:     ListNode* partition(ListNode* pHead, int x) {         // write code here         //创建两个非空链表:小链表和大链表         ListNode* lesstHead,*lesstTail;         lesstHead = lesstTail = (ListNode*)malloc(sizeof(ListNode));          ListNode* greaterHead,*greaterTail;         greaterHead = greaterTail = (ListNode*)malloc(sizeof(ListNode));         //创建临时变量来遍历原数组         ListNode* prev = pHead;         while(prev)         {             //判断当前节点是否小于x             if(prev->val < x)             {                 //插入到小链表中                 lesstTail->next = prev;                 lesstTail = lesstTail->next;             }             else             {                 //插入到大链表中                 greaterTail->next = prev;                 greaterTail = greaterTail->next;             }             prev = prev->next;         }         //退出循环原链表遍历完成         //连接两个链表         lesstTail->next = greaterHead->next;         ListNode* ret = lesstHead->next;         free(lesstHead);         lesstHead = NULL;         free(greaterHead);         greaterHead = NULL;         return ret;     } };

提交结果:

当我们提交代码之后代码有问题,那么代码到底哪里的逻辑不合适呢?我们画图看一下。

/* struct ListNode {     int val;     struct ListNode *next;     ListNode(int x) : val(x), next(NULL) {} };*/ class Partition { public:     ListNode* partition(ListNode* pHead, int x) {         // write code here         //创建两个非空链表:小链表和大链表         ListNode* lesstHead,*lesstTail;         lesstHead = lesstTail = (ListNode*)malloc(sizeof(ListNode));          ListNode* greaterHead,*greaterTail;         greaterHead = greaterTail = (ListNode*)malloc(sizeof(ListNode));         //创建临时变量来遍历原数组         ListNode* prev = pHead;         while(prev)         {             //判断当前节点是否小于x             if(prev->val < x)             {                 //插入到小链表中                 lesstTail->next = prev;                 lesstTail = lesstTail->next;             }             else             {                 //插入到大链表中                 greaterTail->next = prev;                 greaterTail = greaterTail->next;             }             prev = prev->next;         }         //将大链表的尾节点的next指针置为NULL         greaterTail->next = NULL;         //连接两个链表         lesstTail->next = greaterHead->next;         ListNode* ret = lesstHead->next;         free(lesstHead);         lesstHead = NULL;         free(greaterHead);         greaterHead = NULL;         return ret;     } };

提交结果: