Level Order Traversal in C, C++, Java & Python – Code with Explanation & Examples in Short and Simple

   

C Program

#include <stdio.h>
#include <stdlib.h>

struct Node {
    int val;
    struct Node *left, *right;
};

void levelOrder(struct Node* root) {
    struct Node* q[100];
    int front = 0, rear = 0;
    if (root) q[rear++] = root;
    while (front < rear) {
        struct Node* n = q[front++];
        printf("%d ", n->val);
        if (n->left) q[rear++] = n->left;
        if (n->right) q[rear++] = n->right;
    }
}

C Output

Input Tree: [1, 2, 3, 4, 5]
Output: 1 2 3 4 5

C++ Program

#include <iostream>
#include <queue>
using namespace std;

struct Node {
    int val;
    Node *left, *right;
    Node(int v): val(v), left(NULL), right(NULL) {}
};

void levelOrder(Node* root) {
    if (!root) return;
    queue<Node*> q;
    q.push(root);
    while (!q.empty()) {
        Node* n = q.front(); q.pop();
        cout << n->val << " ";
        if (n->left) q.push(n->left);
        if (n->right) q.push(n->right);
    }
}

C++ Output

Input: [1, 2, 3, 4, 5]
Output: 1 2 3 4 5

JAVA Program

import java.util.*;

class Node {
    int val;
    Node left, right;
    Node(int v) { val = v; }
}

void levelOrder(Node root) {
    if (root == null) return;
    Queue<Node> q = new LinkedList<>();
    q.add(root);
    while (!q.isEmpty()) {
        Node n = q.poll();
        System.out.print(n.val + " ");
        if (n.left != null) q.add(n.left);
        if (n.right != null) q.add(n.right);
    }
}

JAVA Output

Input Tree: [1, 2, 3, 4, 5]
Output: 1 2 3 4 5

Python Program

from collections import deque

def levelOrder(root):
    if not root: return
    q = deque([root])
    while q:
        n = q.popleft()
        print(n.val, end=' ')
        if n.left: q.append(n.left)
        if n.right: q.append(n.right)

Python Output

Input: [1, 2, 3, 4, 5]
Output: 1 2 3 4 5

In-Depth Explanation

Example

Take a look at a tree like this:

    1

   / \

  2   3

 / \

4   5

Level order traversal is beginning at the top level and going downward. So, we go 1 → then 2 and 3 → then 4 and 5. The output is 1 2 3 4 5. This is unlike depth-first traversals such as inorder or preorder where we descend deeper before traversing across.

Real-Life Analogy

Consider when individuals depart from a building when there's an emergency. The individuals to depart first are those nearest the door (ground level), followed by those on the first floor, followed by the second. That's precisely the way that level order does things — you handle one floor (level) in its entirety before addressing the next. It's akin to doing a book page by page instead of jumping right into the footnotes.

Why It Matters

Level order traversal is a breadth-first strategy, which prefers nodes near the root over proceeding deep. It's quite helpful in problems where you need to determine how wide or tall the tree is, find nodes at the same level, or even print nodes level-wise. This traversal is the starting point of Breadth-First Search (BFS), which plays an important role in shortest path algorithms, network crawlers, and tree visualization tools.

Learning Insight

This idea familiarizes you with the application of queues in tree traversal — a crucial data structure for breadth-first algorithms. It also instructs structured thinking: instead of exploring one side thoroughly, you work even across levels. This enhances understanding of how to deal with layers in a tree, graph, or system. When you understand this, you can proceed to study more advanced ideas such as level-order zigzag, vertical order, or level sum problems.

Interview Relevance and Real Projects

Level order traversal is an interviewer's best friend since it demonstrates your awareness of queue-based traversal and tree structure. Interviewers can request you to make it return levels as lists, get the max at each level, or check completeness of a binary tree. Real-world applications include rendering UI trees, scheduling jobs, loading game assets, or processing chat threads by priority or hierarchy.

SEO-Optimized Explanation

Level order traversal is also known as a breadth-first traversal of a binary tree, where all nodes are visited level by level from top to bottom. This method uses a queue to process all the nodes at a given level before proceeding to the next. It's a principal method in computer science for hierarchically solving problems in user interface rendering, graph searching, directory listing, and scheduling systems. Mastering level order traversal in C, C++, Java, and Python allows programmers to efficiently deal with tree-based problems, construct scalable systems, and pass coding interviews that concentrate on real-time data processing and nested structures.