题解

c语言

 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 *
 * C语言声明定义全局变量请加上static，防止重复定义
 */

/**
 * 
 * @param pHead1 ListNode类 
 * @param pHead2 ListNode类 
 * @return ListNode类
 */
struct ListNode* Merge(struct ListNode* pHead1, struct ListNode* pHead2 ) {
    // write code here
    struct ListNode *a= pHead1;
        struct ListNode*b= pHead2;
    struct ListNode*start2=(struct ListNode*)malloc(sizeof(struct ListNode));
    start2->next=NULL;
    struct ListNode*start=start2;
    if(a==NULL&&b==NULL)
            return start2->next;
    while(1)
    {  if(a==NULL||b==NULL)
            break;
        struct ListNode *m=start->next=(struct ListNode*)malloc(sizeof(struct ListNode));
        int anum=a->val;
        int bnum=b->val;
        if(anum<=bnum){
         m->val=a->val;
            a=a->next;
        }else{
          m->val=b->val;
            b=b->next;
        }
        start=start->next;
       
    }
    if(!a){
        start->next=b;
    }
    if(!b){
        start->next=a;
    }
    return start2->next;
}