### LeetCode Challenge #21. Merge Two Sorted Lists

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

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

Example 1:

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

Example 2:

```Input: list1 = [], list2 = []
Output: []
```

Example 3:

```Input: list1 = [], list2 = [0]
Output: [0]
```

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.
##### Video Solution
###### Java Solution
```				```
class Solution {
public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
ListNode dummy = new ListNode(-1);
ListNode ans = dummy ;
ListNode ptr1 = list1;
ListNode ptr2 = list2;

while(ptr1!=null && ptr2!=null){
if(ptr1.val<ptr2.val){
dummy.next = ptr1 ;
ptr1 = ptr1.next;
}else {
dummy.next = ptr2 ;
ptr2 = ptr2.next;
}

dummy = dummy.next;
}

if(ptr1==null){
dummy.next = ptr2;
}else{
dummy.next = ptr1 ;
}

return ans.next;
}
}
```
```