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A Data Structure is a way of organizing and storing data so that it can be accessed and modified efficiently.

Different data structures are used for different purposes depending on the type of operations required.

Data structures help improve performance, memory management, and problem-solving in software applications.

• Linear Data Structures
• Non-Linear Data Structures
• Static Data Structures
• Dynamic Data Structures

An Array is a linear data structure used to store multiple values in a single variable.

Array elements are stored in contiguous memory locations and accessed using indexes.

1. Fast access using index
2. Easy traversal
3. Efficient memory usage

const numbers = [10, 20, 30, 40];

console.log(numbers[0]);

numbers.push(50);

console.log(numbers);

A Linked List is a linear data structure where each element is called a node.

Each node contains data and a pointer to the next node in the sequence.

• Dynamic size
• Efficient insertion
• Efficient deletion
• No memory wastage

class Node {
  constructor(data) {
    this.data = data;
    this.next = null;
  }
}

const first = new Node(10);
const second = new Node(20);

first.next = second;

console.log(first);

Stack is a linear data structure that follows the LIFO principle.

LIFO means Last In First Out.

• Undo functionality
• Browser history
• Function call stack
• Expression evaluation

const stack = [];

stack.push(10);
stack.push(20);
stack.push(30);

console.log(stack.pop());
console.log(stack);

Queue is a linear data structure that follows the FIFO principle.

FIFO means First In First Out.

• Task scheduling
• Printer queue
• Call center systems
• CPU scheduling

const queue = [];

queue.push("A");
queue.push("B");
queue.push("C");

console.log(queue.shift());
console.log(queue);

A Hash Table is a data structure that stores data in key-value pairs.

It uses a hash function to calculate the index where data is stored.

• Fast searching
• Fast insertion
• Fast deletion
• Efficient data lookup

const user = {
  id: 1,
  name: "AK",
  city: "Delhi"
};

console.log(user.name);
console.log(user.city);

A Tree is a hierarchical non-linear data structure consisting of nodes.

The top node is called the root node and child nodes are connected below it.

• File systems
• Databases
• HTML DOM
• Search algorithms

class TreeNode {
  constructor(data) {
    this.data = data;
    this.left = null;
    this.right = null;
  }
}

const root = new TreeNode(10);

root.left = new TreeNode(5);
root.right = new TreeNode(20);

console.log(root);

Binary Search is an efficient searching algorithm used on sorted arrays.

It repeatedly divides the search space into two halves.

• Fast searching
• Efficient for large datasets
• Reduces comparisons
• Time Complexity O(log n)

function binarySearch(arr, target) {

  let left = 0;
  let right = arr.length - 1;

  while (left <= right) {

    const mid = Math.floor((left + right) / 2);

    if (arr[mid] === target) {
      return mid;
    }

    if (arr[mid] < target) {
      left = mid + 1;
    } else {
      right = mid - 1;
    }
  }

  return -1;
}

console.log(binarySearch([1,2,3,4,5], 4));

A Graph is a non-linear data structure consisting of nodes and edges.

Graphs are used to represent relationships between different objects.

• Social networks
• Google Maps
• Flight routes
• Recommendation systems

const graph = {
  A: ["B", "C"],
  B: ["D"],
  C: [],
  D: []
};

console.log(graph["A"]);