Print all leaf nodes of a Binary Tree from left to right

Given a binary tree, we need to write a program to print all leaf nodes of the given binary tree from left to right. That is, the nodes should be printed in the order they appear from left to right in the given tree.
For Example,

For the above binary tree, the output will be as shown below:

4 6 7 9 10

The idea to do this is similar to DFS algorithm. Below is a step by step algorithm to do this:

Check if the given node is null. If null, then return from the function.
Check if it is a leaf node. If the node is a leaf node, then print its data.
If in the above step, the node is not a leaf node then check if the left and right children of node exist. If yes then call the function for left and right child of the node recursively.

Below is the implementation of the above approach.

C++

/* C++ program to print leaf nodes from left  
   to right */
#include <iostream> 
using namespace std; 
   
// A Binary Tree Node 
struct Node 
{ 
    int data; 
    struct Node *left, *right; 
}; 
  
// function to print leaf  
// nodes from left to right 
void printLeafNodes(Node *root) 
{ 
    // if node is null, return 
    if (!root) 
        return; 
      
    // if node is leaf node, print its data     
    if (!root->left && !root->right) 
    { 
        cout << root->data << " ";  
        return; 
    } 
  
    // if left child exists, check for leaf  
    // recursively 
    if (root->left) 
       printLeafNodes(root->left); 
          
    // if right child exists, check for leaf  
    // recursively 
    if (root->right) 
       printLeafNodes(root->right); 
}  
  
// Utility function to create a new tree node 
Node* newNode(int data) 
{ 
    Node *temp = new Node; 
    temp->data = data; 
    temp->left = temp->right = NULL; 
    return temp; 
} 
   
// Driver program to test above functions 
int main() 
{ 
    // Let us create binary tree shown in  
    // above diagram 
    Node *root = newNode(1); 
    root->left = newNode(2); 
    root->right = newNode(3); 
    root->left->left = newNode(4); 
    root->right->left = newNode(5); 
    root->right->right = newNode(8); 
    root->right->left->left = newNode(6); 
    root->right->left->right = newNode(7); 
    root->right->right->left = newNode(9); 
    root->right->right->right = newNode(10); 
   
    // print leaf nodes of the given tree 
    printLeafNodes(root); 
      
    return 0; 
} 

Python3

# Python3 program to print  
# leaf nodes from left to right 
  
# Binary tree node 
class Node: 
    
    def __init__(self, data): 
        self.data = data 
        self.left = None
        self.right = None
  
# Function to print leaf 
# nodes from left to right 
def printLeafNodes(root: Node) -> None: 
  
    # If node is null, return 
    if (not root): 
        return
  
    # If node is leaf node,  
    # print its data 
    if (not root.left and 
        not root.right): 
        print(root.data,  
              end = " ") 
        return
  
    # If left child exists,  
    # check for leaf recursively 
    if root.left: 
        printLeafNodes(root.left) 
  
    # If right child exists,  
    # check for leaf recursively 
    if root.right: 
        printLeafNodes(root.right) 
  
# Driver Code 
if __name__ == "__main__": 
  
    # Let us create binary tree shown in 
    # above diagram 
    root = Node(1) 
    root.left = Node(2) 
    root.right = Node(3) 
    root.left.left = Node(4) 
    root.right.left = Node(5) 
    root.right.right = Node(8) 
    root.right.left.left = Node(6) 
    root.right.left.right = Node(7) 
    root.right.right.left = Node(9) 
    root.right.right.right = Node(10) 
  
    # print leaf nodes of the given tree 
    printLeafNodes(root) 
  
# This code is contributed by sanjeev2552

Output:

4 6 7 9 10

Time Complexity: O( n ) , where n is the number of nodes in the binary tree.

This article is contributed by Harsh Agarwal. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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My Personal Notes

C++

Python3

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