合并两个有序链表

1.迭代循环 虚拟头结点typedef struct ListNode ListNode; struct ListNode* mergeTwoLists(struct ListNode* list1, struct ListNode* list2) { if(list1NULL) { return list2; } else if(list2 NULL) { return list1; } else{ ListNode* dum (ListNode*)malloc(sizeof(ListNode)); ListNode* cur dum; while(list1 list2) { if(list1-val list2-val) { cur-next list1; list1 list1-next; } else{ cur-next list2; list2 list2-next; } cur cur-next; } cur-next list1 NULL ? list2 : list1; return dum-next; } }2.递归typedef struct ListNode ListNode; struct ListNode* mergeTwoLists(struct ListNode* list1, struct ListNode* list2) { if(list1NULL) { return list2; } else if(list2 NULL) { return list1; } else if(list1-val list2-val) { list1-next mergeTwoLists(list1-next , list2); return list1; } else { list2-next mergeTwoLists(list2-next , list1); return list2; } }