Select a Random Node from a Singly Linked List

linkedlist/Select a Random Node from a Singly Linked List

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+import java.util.*; 
+
+// Linked List Class 
+class LinkedList { 
+
+    static Node head;  // head of list 
+
+    /* Node Class */
+    static class Node { 
+
+        int data; 
+        Node next; 
+
+        // Constructor to create a new node 
+        Node(int d) { 
+            data = d; 
+            next = null; 
+        } 
+    } 
+
+    // A reservoir sampling based function to print a 
+    // random node from a linked list 
+    void printrandom(Node node) { 
+
+        // If list is empty 
+        if (node == null) { 
+            return; 
+        } 
+
+        // Use a different seed value so that we don't get 
+        // same result each time we run this program 
+        Math.abs(UUID.randomUUID().getMostSignificantBits()); 
+
+        // Initialize result as first node 
+        int result = node.data; 
+
+        // Iterate from the (k+1)th element to nth element 
+        Node current = node; 
+        int n; 
+        for (n = 2; current != null; n++) { 
+
+            // change result with probability 1/n 
+            if (Math.random() % n == 0) { 
+                result = current.data; 
+            } 
+
+            // Move to next node 
+            current = current.next; 
+        } 
+
+        System.out.println("Randomly selected key is " + result); 
+    } 
+
+    // Driver program to test above functions 
+    public static void main(String[] args) { 
+
+        LinkedList list = new LinkedList(); 
+        list.head = new Node(5); 
+        list.head.next = new Node(20); 
+        list.head.next.next = new Node(4); 
+        list.head.next.next.next = new Node(3); 
+        list.head.next.next.next.next = new Node(30); 
+
+        list.printrandom(head); 
+
+    } 
+}