《剑指offer》-合并两个排序的链表

输入两个单调递增的链表，输出两个链表合成后的链表，当然我们需要合成后的链表满足单调不减规则。

class Solution{
public:
    ListNode* Merge(ListNode* pHead1, ListNode* pHead2){
        ListNode* result = NULL;
        ListNode* current = NULL;

        if (pHead1 == NULL){
            return pHead2;
        }
        if (pHead2 == NULL){
            return pHead1;
        }

        while (pHead1 && pHead2){
            if (pHead1->val <= pHead2->val){
                if (result == NULL){
                    current = result = pHead1;
                }
                else{
                    current->next = pHead1;
                    current = current->next;
                }
                pHead1 = pHead1->next;
            }
            else{
                if (result == NULL){
                    current = result = pHead2;
                }
                else{
                    current->next = pHead2;
                    current = current->next;
                }
                pHead2 = pHead2->next;
            }
        }

        if (pHead1){
            current->next = pHead1;
        }
        if (pHead2){
            current->next = pHead2;
        }

        return result;
    }
};