Niuke.com brush questions | merge two sorted linked lists

Topic source: Niuke.com
programming link

Topic description:

Input two monotonically increasing linked lists, and output the linked list after combining the two linked lists. Of course, we need the combined linked list to satisfy the monotonically non-decreasing rule.

Parse:

Use recursive thinking.

Code:

class Solution {
public:
    ListNode* Merge(ListNode* pHead1, ListNode* pHead2)
    {
        if(pHead1 == nullptr)
            return pHead2;
        if(pHead2 == nullptr)
            return pHead1;
        return (pHead1->val > pHead2->val)?(pHead2->next = Merge(pHead1,pHead2->next),pHead2 ):
            (pHead1->next = Merge(pHead1->next,pHead2),pHead1);      
    }
};

Running time: 3ms; Occupied memory: 356k

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Code analysis: first compare the size, determine who is smaller, who is the head node, and the next node of the head node continues to be obtained by merge.
, indicating that the merge is performed first, and then the head node is returned.