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Java Program to Count number of leaf nodes in a tree

Java Program to Count number of leaf nodes in a tree

In this example, we will learn to count the number of leaf nodes in a tree using Java.

To understand this example, you should have the knowledge of the following Java programming topics:


Example: Java Program to count the number of leaf nodes in a tree

class Node {
  int item;
  Node left, right;

  public Node(int key) {
  item = key;
  left = right = null;
  }
}

class Main {
  // root of Tree
  Node root;

  Main() {
  root = null;
  }

  // method to count leaf nodes
  public static int countLeaf(Node node) {
    if(node == null) {
      return 0;
    }

    // if left and right of the node is null
    // it is leaf node
    if (node.left == null && node.right == null) {
      return 1;
    }
    else {
      return countLeaf(node.left) + countLeaf(node.right);
    }
  }

  public static void main(String[] args) {

    // create an object of Tree
    Main tree = new Main();

    // create nodes of tree
    tree.root = new Node(5);
    tree.root.left = new Node(3);
    tree.root.right = new Node(8);

    // create child nodes of left child
    tree.root.left.left = new Node(2);
    tree.root.left.right = new Node(4);

    // create child nodes of right child
    tree.root.right.left = new Node(7);
    tree.root.right.right = new Node(9);

    // call method to count leaf nodes
    int leafNodes = countLeaf(tree.root);
    System.out.println("Total Leaf Nodes = " + leafNodes);
  }
}

Output

Total Leaf Nodes = 4
Treee data structure with 7 nodes and 4 leaf nodes
Count Number of Leaf Nodes

In the above example, we have implemented the tree data structure in Java. Here, we are using recursion to count the number of leaf nodes in the tree.

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