In this problem, we are given a binary tree and we have to print all leaf nodes of the binary tree from right to left.
Let’s take an example to understand the problem
Input −
Output − 7 4 1
To solve this problem, we will have to traverse the binary tree. This traversal can be done in two ways −
Preorder traversal − This traversal uses recursion. Here, we will traverse, root then left and then right subtree. If we encounter a leaf node then we will print it, else we check for children of the node and explore them to find leaf node.
Program to show the implementation of our solution −
#include <iostream> using namespace std; struct Node { int data; struct Node *left, *right; }; Node* insertNode(int data) { Node* temp = new Node; temp->data = data; temp->left = temp->right = NULL; return temp; } void findLeafNode(Node* root) { if (!root) return; if (!root->left && !root->right) { cout<<root->data<<"\t"; return; } if (root->right) findLeafNode(root->right); if (root->left) findLeafNode(root->left); } int main() { Node* root = insertNode(21); root->left = insertNode(5); root->right = insertNode(11); root->left->left = insertNode(8); root->left->right = insertNode(98); root->right->left = insertNode(2); root->right->right = insertNode(8); cout<<"Leaf nodes of the tree from right to left are:\n"; findLeafNode(root); return 0; }
Leaf nodes of the tree from right to left are − 18 2 98 8
Postorder Traversal − This traversal to find the leaf node will use iteration. We will use a stack to store data and traverse the tree in a postorder manner (first right subtree then left subtree and then root) and print leaf nodes.
Program to show the implementation of our solution −
#include<bits/stdc++.h> using namespace std; struct Node { Node* left; Node* right; int data; }; Node* insertNode(int key) { Node* node = new Node(); node->left = node->right = NULL; node->data = key; return node; } void findLeafNode(Node* tree) { stack<Node*> treeStack; while (1) { if (tree) { treeStack.push(tree); tree = tree->right; } else { if (treeStack.empty()) break; else { if (treeStack.top()->left == NULL) { tree = treeStack.top(); treeStack.pop(); if (tree->right == NULL) cout<<tree->data<<"\t"; } while (tree == treeStack.top()->left) { tree = treeStack.top(); treeStack.pop(); if (treeStack.empty()) break; } if (!treeStack.empty()) tree = treeStack.top()->left; else tree = NULL; } } } } int main(){ Node* root = insertNode(21); root->left = insertNode(5); root->right = insertNode(11); root->left->left = insertNode(8); root->left->right = insertNode(98); root->right->left = insertNode(2); root->right->right = insertNode(18); cout<<"Leaf nodes of the tree from right to left are:\n"; findLeafNode(root); return 0; }
Leaf nodes of the tree from right to left are − 18 2 98 8