Create randonNode

randonNode

@@ -0,0 +1,99 @@
+/* C++ program to randomly select a node from a singly
+linked list */
+#include<stdio.h>
+#include<stdlib.h>
+#include <time.h>
+#include<iostream>
+using namespace std;
+
+/* Link list node */
+class Node
+{
+	public:
+	int key;
+	Node* next;
+	void printRandom(Node*);
+	void push(Node**, int);
+
+};
+
+// A reservoir sampling based function to print a
+// random node from a linked list
+void Node::printRandom(Node *head)
+{
+	// IF list is empty
+	if (head == NULL)
+	return;
+
+	// Use a different seed value so that we don't get
+	// same result each time we run this program
+	srand(time(NULL));
+
+	// Initialize result as first node
+	int result = head->key;
+
+	// Iterate from the (k+1)th element to nth element
+	Node *current = head;
+	int n;
+	for (n = 2; current != NULL; n++)
+	{
+		// change result with probability 1/n
+		if (rand() % n == 0)
+		result = current->key;
+
+		// Move to next node
+		current = current->next;
+	}
+
+	cout<<"Randomly selected key is \n"<< result;
+}
+
+/* BELOW FUNCTIONS ARE JUST UTILITY TO TEST */
+
+/* A utility function to create a new node */
+Node* newNode(int new_key)
+{
+	// allocate node
+	Node* new_node = (Node*) malloc(sizeof( Node));
+
+	/// put in the key
+	new_node->key = new_key;
+	new_node->next = NULL;
+
+	return new_node;
+}
+
+/* A utility function to insert a node at the beginning
+of linked list */
+void Node:: push(Node** head_ref, int new_key)
+{
+	/* allocate node */
+	Node* new_node = new Node;
+
+	/* put in the key */
+	new_node->key = new_key;
+
+	/* link the old list off the new node */
+	new_node->next = (*head_ref);
+
+	/* move the head to point to the new node */
+	(*head_ref) = new_node;
+}
+
+// Driver program to test above functions
+int main()
+{
+	Node n1;
+	Node *head = NULL;
+	n1.push(&head, 5);
+	n1.push(&head, 20);
+	n1.push(&head, 4);
+	n1.push(&head, 3);
+	n1.push(&head, 30);
+
+	n1.printRandom(head);
+
+	return 0;
+}
+
+// This code is contributed by SoumikMondal