725. Split Linked List in Parts

 C++

class Solution {
public:
    vector<ListNode*> splitListToParts(ListNode* head, int k) {
        int n = 0;
        for (ListNode* cur = head; cur != nullptr; cur = cur->next) {
            ++n;
        }
        int cnt = n / k, mod = n % k;
        vector<ListNode*> ans(k, nullptr);
        ListNode* cur = head;
        for (int i = 0; i < k && cur != nullptr; ++i) {
            ans[i] = cur;
            int m = cnt + (i < mod ? 1 : 0);
            for (int j = 1; j < m; ++j) {
                cur = cur->next;
            }
            ListNode* nxt = cur->next;
            cur->next = nullptr;
            cur = nxt;
        }
        return ans;
    }
};

JAVA

class Solution {
    public ListNode[] splitListToParts(ListNode root, int k) {
        int n = 0;
        ListNode cur = root;
        while (cur != null) {
            ++n;
            cur = cur.next;
        }
       int width = n / k, remainder = n % k;
        ListNode[] res = new ListNode[k];
        cur = root;
        for (int i = 0; i < k; ++i) {
            ListNode head = cur;
            for (int j = 0; j < width + ((i < remainder) ? 1 : 0) - 1; ++j) {
                if (cur != null) {
                    cur = cur.next;
                }
            }
            if (cur != null) {
                ListNode t = cur.next;
                cur.next = null;
                cur = t;
            }
            res[i] = head;
        }
        return res;
    }
}