Create rotate-list.cpp

beats 96.7

Author: gabedonnan

rotate-list.cpp

@@ -0,0 +1,47 @@
+/**
+ * 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:
+    int getListLength(ListNode* curr) {
+        int fin = 0;
+        while (curr != NULL) {
+            fin++;
+            curr = curr->next;
+        }
+        return fin;
+    }
+
+    ListNode* rotateRight(ListNode* head, int k) {
+        int len = getListLength(head);
+        if (len == 0) {
+            return head;
+        }
+        k = k % len;
+        if (k == 0) {
+            return head;
+        }
+
+        ListNode* secondHalfTail = head;
+        for (int i = 0; i < (len - 1) - k; i++) {
+            secondHalfTail = secondHalfTail->next;
+        }
+        
+
+        ListNode* firstHalfHead = secondHalfTail->next;
+        ListNode* finalVal = firstHalfHead;
+        secondHalfTail->next = NULL;
+        while (firstHalfHead->next != NULL) {
+            firstHalfHead = firstHalfHead->next;
+        }
+        firstHalfHead->next = head;
+        return finalVal;
+    }
+};