cs: add «725. Split Linked List in Parts»

Signed-off-by: Matej Focko <me@mfocko.xyz>

cs/split-linked-list-in-parts.cs

@@ -0,0 +1,39 @@
+public class Solution {
+    private int GetLength(ListNode node) {
+        var count = 0;
+
+        for (; node != null; node = node.next) {
+            ++count;
+        }
+
+        return count;
+    }
+
+    public ListNode[] SplitListToParts(ListNode tail, int k) {
+        var parts = new ListNode[k];
+        Array.Fill(parts, null);
+
+        var listLength = GetLength(tail);
+        var (perPart, leftover) = (listLength / k, listLength % k);
+
+        for (var i = 0; i < k && tail != null; ++i) {
+            var (node, length) = (tail, perPart);
+            parts[i] = node;
+
+            if (leftover > 0) {
+                ++length;
+                --leftover;
+            }
+
+            // Add the regular part
+            for (var j = 0; j < length - 1; ++j) {
+                node = node.next;
+            }
+
+            // Handle the last node in the part as a special case
+            (tail, node.next) = (node.next, null);
+        }
+
+        return parts;
+    }
+}