# Split Linked List In Parts Problem

## Description

LeetCode Problem 725.

The length of each part should be as equal as possible: no two parts should have a size differing by more than one. This may lead to some parts being null.

The parts should be in the order of occurrence in the input list, and parts occurring earlier should always have a size greater than or equal to parts occurring later.

Return an array of the k parts.

Example 1:

``````1
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Input: head = [1,2,3], k = 5
Output: [,,,[],[]]
Explanation:
The first element output has output.val = 1, output.next = null.
The last element output is null, but its string representation as a ListNode is [].
``````

Example 2:

``````1
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Input: head = [1,2,3,4,5,6,7,8,9,10], k = 3
Output: [[1,2,3,4],[5,6,7],[8,9,10]]
Explanation:
The input has been split into consecutive parts with size difference at most 1, and earlier parts are a larger size than the later parts.
``````

Constraints:

• The number of nodes in the list is in the range [0, 1000].
• 0 <= Node.val <= 1000
• 1 <= k <= 50

## Sample C++ Code

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/**
* 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:
vector<ListNode*> splitListToParts(ListNode* root, int k) {
//first calculate the length
int len = 0;
ListNode* temp  =root;
while (temp) {
len ++;
temp = temp->next;
}

int numNodes = len / k; //the number of nodes that are to be in each group
int extra = len % k;  //the extra nodes that are left
int i = 0;
vector<ListNode*> res;
temp = root;
while (temp) {
res.push_back(temp);
//get the numNodes and make the last node next to NULL
int currLen = 1;
while (currLen < numNodes) {
temp = temp->next;
currLen ++;
}
if (extra > 0 && len > k) {
temp = temp->next;
extra --;
}
ListNode* x = temp->next;
temp->next = NULL;
temp = x;
}
//if the number of nodes are less than k we add NULL
while (len < k) {
res.push_back(NULL);
len ++;
}
return res;
}
};
``````