[LeetCode] Merge Two Sorted Lists

Merge Two Sorted Lists

这貌似也一个常见的面试题.合并两个有序链表.尽量的占用空间少。

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

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• 解法： 用一个指针在两个链表上移动，一直next下去连成一串，就是答案.为了方便，使用上一篇的那种方法，建一个超级头结点，从这个头结点开始移动写起来会比较方便.不用判断第一个节点是在l1还是l2。

Code:

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
    void moveToList(ListNode* &pkMove, ListNode* &pkTgtList) {
        if (!pkTgtList) return;
        pkMove->next = pkTgtList;
        pkTgtList = pkTgtList->next;
        pkMove = pkMove->next;
    }
public:
    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
        ListNode* pkResult = new ListNode(0);
        ListNode* pkMove = pkResult;
        for (; l1 && l2; moveToList(pkMove, l1->val < l2->val ? l1 : l2));
        moveToList(pkMove, l1);
        moveToList(pkMove, l2);

        return pkResult->next;
    }
};

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