---
title: 'LeetCode 21. Merge Two Sorted Lists'
disqus: hackmd
---

# LeetCode 21. Merge Two Sorted Lists

## Description

You are given the heads of two sorted linked lists list1 and list2.

Merge the two lists in a one sorted list. The list should be made by splicing together the nodes of the first two lists.

Return the head of the merged linked list.

## Example

Input: list1 = [1,2,4], list2 = [1,3,4]
Output: [1,1,2,3,4,4]

## Constraints

The number of nodes in both lists is in the range [0, 50].
-100 <= Node.val <= 100
Both list1 and list2 are sorted in non-decreasing order.

## Answer

此題可藉由取餘數將每個數字都抓出，然後再做前後比對，而INT最大就是10位數。

struct ListNode* mergeTwoLists(struct ListNode* l1, struct ListNode* l2){
    if(l1 == NULL){return l2;}
    if(l2 == NULL){return l1;}
    struct ListNode *ans = NULL, *opr = NULL;
    if(l1->val > l2->val){
        opr = l2;
        l2 = l2->next;
    }
    else{
        opr = l1;
        l1 = l1->next;
    }
    ans = opr;
    while(l1 && l2){
        if(l1->val > l2->val){
            opr->next = l2;
            l2 = l2->next;
        }
        else{
            opr->next = l1;
            l1 = l1->next;
        }
        opr = opr->next;
    }
    if(l1){opr->next = l1;}
    if(l2){opr->next = l2;}
    return ans;
}

## Link
https://leetcode.com/problems/merge-two-sorted-lists/
###### tags: `Leetcode`