Search a node in Binary tree

Abhishek Kumar • Category: Data Structures • Tags: datastructures binary-tree

Search a node in a Binary tree using recursion or iterative solution. For example, a binary tree contains the following elements-
1, 2, 3, 4, 5, 6, 7
Here, if 7 is searched then return true but if 9 is searched then return false because it is not available in the binary tree.

In a Binary Tree, to search a node we have to traverse each node and check if that node is available in the tree.

We can solve this problem in two ways-

Recursive solution
Iterative solution

Recursive solution

For recursive solution we have to check each node one by one recursively as we have done in binary tree recursive traversal and if required node is found then return True otherwise return False.

Python
Javascript

class Node:
    def __init__(self, data):
        self.left = None
        self.data = data
        self.right = None

def search_node(root, num):
    if root is None:
        return False
    if root.data == num:
        return True
    val = search_node(root.left, num)
    if val:
        return True
    return search_node(root.right, num)

root = Node(1)
root.left = Node(2)
root.right = Node(3)
root.left.left = Node(4)
root.left.right = Node(5)
root.right.left = Node(6)
root.right.right = Node(7)
print(search_node(root, 7))

class Node {
  constructor(data) {
    this.left = null;
    this.data = data;
    this.right = null;
  }
}

function searchNode(root, num) {
  if (!root) return false;
  if (root.data === num) return true;
  let val = searchNode(root.left, num);
  if (val) return true;
  return searchNode(root.right, num);
}

const root = new Node(1);
root.left = new Node(2);
root.right = new Node(3);
root.left.left = new Node(4);
root.left.right = new Node(5);
root.right.left = new Node(6);
root.right.right = new Node(7);
console.log(searchNode(root, 7));

Output

True

Iterative solution

For iterative solution, we have to traverse each node in level order and if required node is found then return True otherwise return False.

Python
Javascript

import queue

class Node:
    def __init__(self, data):
        self.left = None
        self.data = data
        self.right = None

def search_node(root, num):
    if root is None:
        return False
    q = queue.Queue()
    q.put(root)
    while not q.empty():
        node = q.get()
        if node.data == num:
            return True
        if node.left:
            q.put(node.left)
        if node.right:
            q.put(node.right)
    return False

root = Node(1)
root.left = Node(2)
root.right = Node(3)
root.left.left = Node(4)
root.left.right = Node(5)
root.right.left = Node(6)
root.right.right = Node(7)
print(search_node(root, 7))

class Node {
  constructor(data) {
    this.left = null;
    this.data = data;
    this.right = null;
  }
}

function searchNode(root, num) {
  if (!root) return false;

  const q = [];
  q.push(root);

  while (q.length > 0) {
    let node = q.shift();
    if (node.data === num) return true;
    if (node.left) q.push(node.left);
    if (node.right) q.push(node.right);
  }
  return false;
}

const root = new Node(1);
root.left = new Node(2);
root.right = new Node(3);
root.left.left = new Node(4);
root.left.right = new Node(5);
root.right.left = new Node(6);
root.right.right = new Node(7);
console.log(searchNode(root, 7));