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* pHead1, struct ListNode* pHead2 ) {
    // write code here 
    
    if (pHead1 == NULL) {
        return pHead2;
    }
    if (pHead2 == NULL ) {
        return pHead1;
    }
    struct ListNode* a=pHead1;
    struct ListNode* b=pHead2;
    struct ListNode* head;
    
    if (a->val < b->val) {
        head=a;
        a=a->next;
    }else {
        head=b;
        b=b->next;
    }
    struct ListNode* tail=head;
    while (a!=NULL && b!=NULL) {
        if (a->val < b->val) {
            tail->next=a;
            a=a->next;
        }else {
            tail->next =b; 
            b=b->next;
        }
         tail=tail->next;
    }
   
    if (a!=NULL) {
        tail->next=a;
    }
    if(b!=NULL){
        tail->next =b;
    }
    return head;
   
}