From 9d8c5828941723e91c519d892a1518f5ee447adf Mon Sep 17 00:00:00 2001
From: narender08 <56318863+narender08@users.noreply.github.com>
Date: Sat, 23 Oct 2021 11:47:17 +0530
Subject: [PATCH] Create removeLoopFromLinkList

---
 removeLoopFromLinkList | 115 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 removeLoopFromLinkList

diff --git a/removeLoopFromLinkList b/removeLoopFromLinkList
new file mode 100644
index 0000000..89e8d3a
--- /dev/null
+++ b/removeLoopFromLinkList
@@ -0,0 +1,115 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+/* Link list node */
+struct Node {
+	int data;
+	struct Node* next;
+};
+
+/* Function to remove loop. */
+void removeLoop(struct Node*, struct Node*);
+
+/* This function detects and removes loop in the list
+If loop was there in the list then it returns 1,
+otherwise returns 0 */
+int detectAndRemoveLoop(struct Node* list)
+{
+	struct Node *slow_p = list, *fast_p = list;
+
+	// Iterate and find if loop exists or not
+	while (slow_p && fast_p && fast_p->next) {
+		slow_p = slow_p->next;
+		fast_p = fast_p->next->next;
+
+		/* If slow_p and fast_p meet at some point then there
+		is a loop */
+		if (slow_p == fast_p) {
+			removeLoop(slow_p, list);
+
+			/* Return 1 to indicate that loop is found */
+			return 1;
+		}
+	}
+
+	/* Return 0 to indicate that there is no loop*/
+	return 0;
+}
+
+/* Function to remove loop.
+loop_node --> Pointer to one of the loop nodes
+head --> Pointer to the start node of the linked list */
+void removeLoop(struct Node* loop_node, struct Node* head)
+{
+	struct Node* ptr1 = loop_node;
+	struct Node* ptr2 = loop_node;
+
+	// Count the number of nodes in loop
+	unsigned int k = 1, i;
+	while (ptr1->next != ptr2) {
+		ptr1 = ptr1->next;
+		k++;
+	}
+
+	// Fix one pointer to head
+	ptr1 = head;
+
+	// And the other pointer to k nodes after head
+	ptr2 = head;
+	for (i = 0; i < k; i++)
+		ptr2 = ptr2->next;
+
+	/* Move both pointers at the same pace,
+	they will meet at loop starting node */
+	while (ptr2 != ptr1) {
+		ptr1 = ptr1->next;
+		ptr2 = ptr2->next;
+	}
+
+	// Get pointer to the last node
+	while (ptr2->next != ptr1)
+		ptr2 = ptr2->next;
+
+	/* Set the next node of the loop ending node
+	to fix the loop */
+	ptr2->next = NULL;
+}
+
+/* Function to print linked list */
+void printList(struct Node* node)
+{
+	// Print the list after loop removal
+	while (node != NULL) {
+		cout << node->data << " ";
+		node = node->next;
+	}
+}
+
+struct Node* newNode(int key)
+{
+	struct Node* temp = new Node();
+	temp->data = key;
+	temp->next = NULL;
+	return temp;
+}
+
+// Driver Code
+int main()
+{
+	struct Node* head = newNode(50);
+	head->next = newNode(20);
+	head->next->next = newNode(15);
+	head->next->next->next = newNode(4);
+	head->next->next->next->next = newNode(10);
+
+	/* Create a loop for testing */
+	head->next->next->next->next->next = head->next->next;
+
+	detectAndRemoveLoop(head);
+
+	cout << "Linked List after removing loop \n";
+	printList(head);
+	return 0;
+}
+
+// This code has been contributed by Striver