leetcode-21-c语言

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* mergeTwoLists(struct ListNode* l1, struct ListNode* l2) {
    struct ListNode *ans,*p;
    if(!l1){
    	return l2;
    }
    else if(!l2){
    	return l1;
    }

    if(l1->val<=l2->val){
    	ans=l1;
    	l1=l1->next;
    }else{
    	ans=l2;
    	l2=l2->next;
    }
    p=ans;

    while(l1&&l2){
    	if(l1->val<=l2->val){
    		p->next=l1;
    		l1=l1->next;
    	}else{
    		p->next=l2;
    		l2=l2->next;
    	}
    	p=p->next;
    }
    if(!l1){
    	p->next=l2;
    }else{
    	p->next=l1;
    }
    return ans;
}