题解 | #合并两个排序的链表#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */
/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param pHead1 ListNode类 
 * @param pHead2 ListNode类 
 * @return ListNode类
 */
struct ListNode* Merge(struct ListNode* l1, struct ListNode* l2 ) {
    if(l1 ==NULL){
        return l2;
    }
    if(l2 == NULL){
        return l1;
    }
    struct ListNode* head = NULL,*tail = NULL;
    while(l1&&l2){
        if(l1->val<l2->val){
            if(head == NULL){
                head = tail = l1;
            }
            else{
                tail->next = l1;
                tail = l1;
            }
            l1 =l1->next;
        }
        else{
            if(head == NULL){
                head = tail = l2;
            }
            else{
                tail->next = l2;
                tail = l2;
            }
            l2 =l2->next;
        }
    }
    if(l1 != NULL){
        tail->next = l1;
    }
    if(l2 != NULL){
        tail->next = l2;
    }
    return head;
}