93 lines
2.4 KiB
Java
93 lines
2.4 KiB
Java
/** Author : Suraj Kumar
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* Github : https://github.com/skmodi649
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*/
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/** PROBLEM DESCRIPTION :
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* There is a single linked list and we are supposed to find a random node in the given linked list
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*/
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/** ALGORITHM :
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* Step 1 : START
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* Step 2 : Create an arraylist of type integer
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* Step 3 : Declare an integer type variable for size and linked list type for head
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* Step 4 : We will use two methods, one for traversing through the linked list using while loop and also increase the size by 1
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*
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* (a) Algorithms_random_node(head)
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* (b) run a while loop till null;
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* (c) add the value to arraylist;
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* (d) increase the size;
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*
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* Step 5 : Now use another method for getting random values using Math.random() and return the value present in arraylist for the calculated index
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* Step 6 : Now in main() method we will simply insert nodes in the linked list and then call the appropriate method and then print the random node generated
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* Step 7 : STOP
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*/
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package com.company;
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import java.util.ArrayList;
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public class Algorithms_random_node {
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ArrayList<Integer> list;
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int size;
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static ListNode head;
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static class ListNode{
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int val;
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ListNode next;
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ListNode(int val){
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this.val = val;
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}
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}
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public Algorithms_random_node(ListNode head) {
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list = new ArrayList<>();
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size = 0;
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ListNode temp = head;
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//Now using while loop to traverse through the linked list and
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//go on adding values and increasing the size value by 1
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while (temp != null) {
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list.add(temp.val);
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temp=temp.next;
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size++;
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}
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}
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public int getRandom() {
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int index = (int)(Math.random()*size);
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return list.get(index);
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}
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// Driver program to test above functions
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public static void main(String[] args) {
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head = new ListNode(15);
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head.next = new ListNode(25);
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head.next.next = new ListNode(4);
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head.next.next.next = new ListNode(1);
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head.next.next.next.next = new ListNode(78);
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head.next.next.next.next.next = new ListNode(63);
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Algorithms_random_node list = new Algorithms_random_node(head);
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int random_num = list.getRandom();
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System.out.println("Random Node : "+random_num);
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}
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}
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/** OUTPUT :
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* First output :
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* Random Node : 25
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* Second output :
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* Random Node : 78
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*/
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/** Time Complexity : O(n)
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* Auxiliary Space Complexity : O(1)
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*/
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