Print First Shortest Root to Leaf Path in a Binary Tree Using C++

In this tutorial, we will be discussing a program to print the first shortest root to leaf path in a Binary Tree.

In this, we will be given a binary tree with distinct values, and we have to find the shortest path from the root node to the leaf node in a given binary tree.

To solve this, we can use a queue to perform level order traversal in a binary tree and store the nodes in the shortest path. For this, once we reach the leftmost node for the final level, we retrieve the values from the queue and print the shortest path.

Example

#include <bits/stdc++.h>
using namespace std;
struct Node{
   struct Node* left;
   struct Node* right;
   int data;
};
struct Node* create_node(int data){
   struct Node* temp = new Node;
   temp->data = data;
   temp->left = NULL;
   temp->right = NULL;
   return temp;
}
void print_spath(int Data, unordered_map<int, int> parent){
   if (parent[Data] == Data)
      return;
   print_spath(parent[Data], parent);
   cout << parent[Data] << " ";
}
void leftmost_path(struct Node* root){
   queue<struct Node*> q;
   q.push(root);
   int LeafData = -1;
   struct Node* temp = NULL;
   unordered_map<int, int> parent;
   parent[root->data] = root->data;
   while (!q.empty()){
      temp = q.front();
      q.pop();
      if (!temp->left && !temp->right){
         LeafData = temp->data;
      break;
      }
      else{
         if (temp->left){
            q.push(temp->left);
            parent[temp->left->data] = temp->data;
         }
         if (temp->right) {
            q.push(temp->right);
            parent[temp->right->data] = temp->data;
         }
      }
   }
   print_spath(LeafData, parent);
   cout << LeafData << " ";
}
int main(){
   struct Node* root = create_node(21);
   root->left = create_node(24);
   root->right = create_node(35);
   root->left->left = create_node(44);
   root->right->left = create_node(53);
   root->right->right = create_node(71);
   root->left->left->left = create_node(110);
   root->left->left->right = create_node(91);
   root->right->right->left = create_node(85);
   leftmost_path(root);
   return 0;
}

Output

21 35 53