### LeetCode Challenge #2130. Maximum Twin Sum of a Linked List

In a linked list of size `n`, where `n` is even, the `ith` node (0-indexed) of the linked list is known as the twin of the `(n-1-i)th` node, if `0 <= i <= (n / 2) - 1`.

• For example, if `n = 4`, then node `0` is the twin of node `3`, and node `1` is the twin of node `2`. These are the only nodes with twins for `n = 4`.

The twin sum is defined as the sum of a node and its twin.

Given the `head` of a linked list with even length, return the maximum twin sum of the linked list.

Example 1:

```Input: head = [5,4,2,1]
Output: 6
Explanation:
Nodes 0 and 1 are the twins of nodes 3 and 2, respectively. All have twin sum = 6.
There are no other nodes with twins in the linked list.
Thus, the maximum twin sum of the linked list is 6.
```

Example 2:

```Input: head = [4,2,2,3]
Output: 7
Explanation:
The nodes with twins present in this linked list are:
- Node 0 is the twin of node 3 having a twin sum of 4 + 3 = 7.
- Node 1 is the twin of node 2 having a twin sum of 2 + 2 = 4.
Thus, the maximum twin sum of the linked list is max(7, 4) = 7.
```

Example 3:

```Input: head = [1,100000]
Output: 100001
Explanation:
There is only one node with a twin in the linked list having twin sum of 1 + 100000 = 100001.
```

Constraints:

• The number of nodes in the list is an even integer in the range `[2, 105]`.
• `1 <= Node.val <= 105`
##### Video Solution
###### C++ Solution
```				```
class Solution {
public:

// either reverse the linkedList and calculate or
// save it in a vector and calculate

vector<int> v;

{
}

if(v.size()==1)return v[0];
int i=0,j=v.size()-1;
int maxSum=INT_MIN;
while(i<j)
{
maxSum=max(maxSum, v[i]+v[j]);
i++;
j--;
}
return maxSum;
}
};
```
```