86 Partition List

/*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.注意：    当在第一个节点需要调整时，head->val >=val时，需要在head之前插入节点需要一个head_r*//** * Definition for singly-linked list. * struct ListNode { *     int val; *     struct ListNode *next; * }; */struct ListNode* partition(struct ListNode* head, int x){if(!head) return head;    struct ListNode *head_r=(struct ListNode*)malloc(sizeof(struct ListNode));head_r->next=head;struct ListNode *insert_r=head_r;struct ListNode *fast=head;while(insert_r->next && insert_r->next->val < x)//寻找第一个不小于x的前一个节点{insert_r=insert_r->next;}struct ListNode *fast_r=insert_r;fast=insert_r->next;//第一个不小于x的节点while(fast){if(fast->val >= x){fast_r=fast;fast=fast->next;}else{fast_r->next=fast->next;fast->next=insert_r->next;insert_r->next=fast;insert_r=fast;fast=fast_r->next;}}return head_r->next;}struct ListNode* partition(struct ListNode* head, int x){if(!head) return head;    struct ListNode *head_r=(struct ListNode*)malloc(sizeof(struct ListNode));head_r->next=NULL;struct ListNode *h_r=head_r;    struct ListNode *head_b=(struct ListNode*)malloc(sizeof(struct ListNode));head_b->next=NULL;struct ListNode *h_b=head_b;struct ListNode *tmp=head;while(tmp){if(tmp->val < x){h_r->next=tmp;h_r=h_r->next;}else{h_b->next=tmp;h_b=h_b->next;}tmp=tmp->next;}h_b->next=NULL;h_r->next=head_b->next;return head_r->next;}