Merge Two Sorted Lists

Posted 2020-07-04

注意是sorted，两个以排序好的。主要区分情况就能做完

 

class Solution {
public:
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {

　　if(l1 == NULL) {
　　　　return l2;
　　}
　　if(l2 == NULL) {
　　　　return l1;
　　}
ListNode* p1;
ListNode* p2;
if(l1->val > l2->val) {
p1 = l1;
p2 = l2;
}
else {
p1 = l2;
p2 = l1;
}
ListNode* head = p2;
while(p2->next != NULL) {
//不存在p2是尾结点
if(p1->val > p2->next->val) {
p2 = p2->next;
continue;
}
else {
if(p1->next == NULL) {
p1->next = p2->next;
p2->next = p1;
return head;
}
ListNode* q = p1;
p1 = p1->next;
q->next = p2->next;
p2->next = q;
continue;
}
}
//如果p2是尾结点
p2->next = p1;
return head;
}
};