Create: 0061-rotate-list.cpp

Author: gautham-8

cpp/0061-rotate-list.cpp

@@ -0,0 +1,45 @@
+/*
+    Given the head of a linked list, rotate the list to the right by k places.
+    Example: list = [1,2,3,4,5] and k = 2
+    Output: [4,5,1,2,3]
+    
+    Time complexity: O(n)
+    Space complexity: O(1)
+*/
+
+class Solution {
+private:
+    int findLen(ListNode* head){
+        int len = 0;
+        while(head!=NULL){
+            len++;
+            head = head->next;
+        }
+        return len;
+    }
+    ListNode* findNewHead(ListNode* head,int k){
+        int i=0;
+        while(i+1<k){
+            i++;
+            head = head->next;
+        }
+        ListNode* ret = head->next;
+        head->next = NULL;
+        return ret;
+    }
+    ListNode* findLast(ListNode* head){
+        while(head->next!=NULL) head = head->next;
+        return head;
+    }
+public:
+    ListNode* rotateRight(ListNode* head, int k) {
+        int len = findLen(head); // Finds the length of the Linked List
+        if(len==0) return head;
+        k = k%len;
+        if(k==0) return head;
+        ListNode* newHead = findNewHead(head,len-k); // Finds the node that is the new head
+        ListNode* last = findLast(newHead); // Finds the last node from the new head and connects it to the previous head
+        last->next = head;
+        return newHead;
+    }
+};