725. Split Linked List in Parts

Hint

/**
 * Definition for singly-linked list.
 * 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* head, int k)
    {
        int n = 0;
        ListNode* cur = head;
        while (cur)
        {
            n++;
            cur = cur->next;
        }

        int splitSize = n / k;
        int remaining = n % k;

        vector<ListNode*> res(k);
        cur = head;
        for (int i = 0; i < k; i++)
        {
            ListNode* partHead = cur;
            int partSize = splitSize + (remaining > 0 ? 1 : 0);
            remaining--;

            for (int j = 0; j < partSize - 1 && cur; j++)
            {
                cur = cur->next;
            }

            if (cur) {
                ListNode* nextPart = cur->next;
                cur->next = nullptr;
                cur = nextPart;
            }
            res[i] = (partHead);
        }
        return res;
    }
};

• T: $O(n)$
• S: $O(n)$