mege_sorted_list

  • 2022-12-14
  • 浏览 (545)

mege_sorted_list.cpp 源码

//
// Created by roseduan on 2021/9/20.
// 合并两个有序链表
//

struct ListNode {
    int val;
    ListNode *next;

    ListNode() : val(0), next(nullptr) {}
    ListNode(int x) : val(x), next(nullptr) {}
    ListNode(int x, ListNode *next) : val(x), next(next) {}
};

class Solution {
public:
    // 迭代法
    ListNode* mergeTwoLists1(ListNode* l1, ListNode* l2) {
        auto dummy = new ListNode();
        auto p = dummy;
        while (l1 && l2) {
            if (l1->val < l2->val) {
                p->next = l1;
                l1 = l1->next;
            } else {
                p->next = l2;
                l2 = l2->next;
            }
            p = p->next;
        }
        p->next = l1 ? l1 : l2;
        return dummy->next;
    }

    // 递归
    ListNode* mergeTwoLists2(ListNode* l1, ListNode* l2) {
        if (l1 == nullptr) {
            return l2;
        }
        if (l2 == nullptr) {
            return l1;
        }
        if (l1->val < l2->val) {
            l1->next = mergeTwoLists2(l1->next, l2);
            return l1;
        } else {
            l2->next = mergeTwoLists2(l1, l2->next);
            return l2;
        }
    }
};

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