LeetCode算法学习(9)

题目描述

Merge Two Sorted Lists
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.

Example:

Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

题目大意

对两个排好序的链表进行合并。

思路分析

分别遍历，把较小的结点加入到链表中。

关键代码

    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
        ListNode *p = l1, *q = l2;
        ListNode *lm = new ListNode(-1);
        ListNode *pm = lm;
        while (p != NULL && q != NULL) {
            if (p->val >= q->val) {
                pm->next = new ListNode(q->val);
                pm = pm->next;
                q = q->next;
            } else {
                pm->next = new ListNode(p->val);
                pm = pm->next;
                p = p->next;
            }
        }
        while (p != NULL) {
            pm->next = new ListNode(p->val);
            pm = pm->next;
            p = p->next;
        }
        while (q != NULL) {
            pm->next = new ListNode(q->val);
            pm = pm->next;
            q = q->next;
        }
        return lm->next;
    }

总结

嗯，这次复习了链表。