110 lines
3.0 KiB
Java
110 lines
3.0 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 Binary Search Tree given and we are supposed to find a random node in the given binary tree.
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*/
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/** ALGORITHM :
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* Step 1: START
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* Step 2: First create a binary tree using the steps mentioned in the first approach
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* Step 3: Now use a method inOrder() that takes a node as input parameter to traverse through the
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* binary tree in inorder fashion as also store the values in a ArrayList simultaneously.
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* Step 4: Now define a method getrandom() that takes a node as input parameter, in this first call
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* the inOrder() method to store the values in the arraylist, then find the size of the binary tree and now just generate a random number between 0 to n-1.
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* Step 5: After generating the number display the value of the ArrayList at the generated index
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* Step 6: STOP
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*/
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import java.util.ArrayList;
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// Using auxiliary array to find the random node in a given binary tree
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class Node {
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int item;
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Node left, right;
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public Node(int key) {
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item = key;
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left = right = null;
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}
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}
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class Tree {
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// Using a arraylist to store the inorder traversal of the given binary tree
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static ArrayList<Integer> list = new ArrayList<Integer>();
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// root of Tree
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Node root;
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Tree() {
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root = null;
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}
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// Now lets find the inorder traversal of the given binary tree
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static void inOrder(Node node) {
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if (node == null)
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return;
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// traverse the left child
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inOrder(node.left);
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list.add(node.item);
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// traverse the right child
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inOrder(node.right);
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}
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public void getrandom(Node val)
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{
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inOrder(val);
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// getting the count of node of the binary tree
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int n = list.size();
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int min = 0;
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int max = n - 1;
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//Generate random int value from 0 to n-1
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int b = (int)(Math.random()*(max-min+1)+min);
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// displaying the value at the generated index
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int random = list.get(b);
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System.out.println("Random Node : " + random);
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}
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public static void main(String[] args) {
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Tree tree = new Tree();
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tree.root = new Node(1);
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tree.root.left = new Node(12);
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tree.root.right = new Node(9);
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tree.root.left.left = new Node(5);
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tree.root.left.right = new Node(6);
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tree.getrandom(tree.root);
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}
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}
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/** Explanation of the Approach :
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* (a) Form the required binary tree
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* (b) Now use the inOrder() method to get the nodes in inOrder fashion and also store them in the given arraylist 'list'
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* (c) Using the getRandom() method generate a random number between 0 to n-1, then get the value at the generated random number
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* from the arraylist using get() method and finally display the result.
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*/
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/** OUTPUT :
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* First output :
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* Random Node : 15
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* Second output :
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* Random Node : 99
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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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