題目描述
輸入兩個單調遞增的鏈表,輸出兩個鏈表合成後的鏈表,當然我們需要合成後的鏈表滿足單調不減規則。
遞歸方法:
/*
struct ListNode {
int val;
struct ListNode *next;
ListNode(int x) :
val(x), next(NULL) {
}
};*/
class Solution {
public:
ListNode* Merge(ListNode* pHead1, ListNode* pHead2)
{
if(pHead1==NULL){return pHead2;}
if(pHead2==NULL){return pHead1;}
if(pHead1->val<=pHead2->val)
{
pHead1->next=Merge(pHead1->next, pHead2);
return pHead1;
}
else
{
pHead2->next=Merge(pHead1,pHead2->next);
return pHead2;
}
}
};
非遞歸算法
/*
struct ListNode {
int val;
struct ListNode *next;
ListNode(int x) :
val(x), next(NULL) {
}
};*/
class Solution {
public:
ListNode* Merge(ListNode* pHead1, ListNode* pHead2)
{
if(pHead1==NULL){return pHead2;}
if(pHead2==NULL){return pHead1;}
ListNode* list=NULL;
ListNode* current=NULL;
while(pHead1!=NULL&&pHead2!=NULL)
{
if(pHead1->val<=pHead2->val)
{
if(list==NULL)
{
list=current=pHead1;
}
else
{
current->next=pHead1;
current=current->next;
}
pHead1=pHead1->next;
}
else
{
if(current==NULL)
{
list=current=pHead2;
}
else
{
current->next=pHead2;
current=current->next;
}
pHead2=pHead2->next;
}
}
if(pHead1==NULL){current->next=pHead2;}
else if(pHead2==NULL){current->next=pHead1;}
return list;
}
};