Array in DSA

 

🔢 Array Kya Hota Hai?

Array ek linear data structure hai jisme ek jaise data types ke elements ek saath contiguous memory locations par store kiye jaate hain. Ye programming mein sabse simple aur frequently used structure hai.

✅ Example:

int arr[5] = {10, 20, 30, 40, 50};

Yahan arr ek array hai jisme 5 integers store hain. Har element ka ek index hota hai jiske through hum usse access kar sakte hain.

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🧠 Basic Terminologies of Array

1. Array Index

• Array ke elements ko access karne ke liye indexing ka use hota hai.

• Indexing 0 se start hoti hai.

• Agar array ke 5 elements hain, to unke indexes 0 se 4 tak honge.

➡️ Example: arr[0] = 10, arr[1] = 20, ...

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2. Array Element

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• Array ke andar har ek individual value ko element kehte hain.

• Har element ek specific index pe hota hai.

• Hum kisi bhi index ka use karke directly us element ko access kar sakte hain.

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3. Array Length

• Array ki length ya size usmein present total elements batata hai.

• Agar array mein 10 items hain, to uski length 10 hogi.

• Ye fixed hoti hai (static array ke case mein), aur declare karte waqt decide hoti hai.

➡️ Example: int arr[10]; → Length = 10

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🧠 Memory Representation of Array

• Array ke saare elements memory mein ek ke baad ek (contiguously) store hote hain.

• Iska matlab hai agar pehla element kisi memory address pe store hua hai (maan lo 1000), aur har element ka size 4 bytes hai, to next elements 1004, 1008, 1012... pe store honge.

🧠 Iska Fayda?

• Hum kisi bhi element ko directly access kar sakte hain using formula:

  
  address(arr[i]) = base_address + (i * size_of_each_element)
  

• Ye technique random access ko possible banati hai in O(1) time, jo array ko efficient banata hai for reading or writing.

🔶 Array Kya Hota Hai?

Array ek linear data structure hai jo same type ke elements ko contiguous (lagataar) memory locations mein store karta hai. Jaise ki ek list ho jisme sirf integers ya characters hi ho sakte hain.

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🔸 Basic Terms (Basic Shabdavali)

• Index: Array mein har element ka ek position number hota hai, jise index kehte hain. Index hamesha 0 se start hota hai.

• Element: Array ke andar rakha gaya item (jaise 10, 20, 'a' etc.)

• Length/Size: Array mein total kitne elements store ho sakte hain, usse uska size ya length kehte hain.

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🔸 Memory Representation

Array ke elements ek ke baad ek memory mein store hote hain. Is wajah se unhe direct access kiya ja sakta hai using index.

Example:

c
int arr[] = {10, 20, 30};

Yahan arr[0] = 10, arr[1] = 20, arr[2] = 30.

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🔸 Declaration of Array

Different programming languages mein array declare karne ka tareeka alag hota hai:

c
int arr[5];        // 5 integers store honge
char name[10];     // 10 characters
float prices[20];  // 20 floating point numbers

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🔸 Initialization of Array

Array ko declare karne ke saath initialize bhi kar sakte ho:

c
int arr[] = {1, 2, 3, 4, 5};
char vowels[5] = {'a', 'e', 'i', 'o', 'u'};

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🔸 Array Ki Zarurat Kyun Padti Hai?

Agar ek class mein 100 students hain aur unke marks store karne ho, to 100 alag-alag variables banana bahut mushkil ho jaayega. Array ki madad se hum ek hi variable mein multiple values store kar sakte hain.

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🔶 Types of Arrays

1. Size ke basis par:

✅ Fixed Size Array

• Size program likhne ke time decide karna padta hai.

• Memory compile time par allocate hoti hai.

c
int arr[5];               // fixed size
int arr2[5] = {1,2,3,4,5}; // initialized

✅ Dynamic Size Array

• Size run-time pe decide hota hai.

• Memory dynamically allocate hoti hai.

cpp
vector<int> v;  // C++ STL

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2. Dimensions ke basis par:

✅ One-Dimensional Array (1-D)

Ek straight line jaise array. Jaise ek row of numbers.

c

int arr[5] = {10, 20, 30, 40, 50};

✅ Two-Dimensional Array (2-D) – Matrix

Rows aur columns mein data store karna.

c

int matrix[2][3] = {
   {1, 2, 3},
   {4, 5, 6}
};

✅ Three-Dimensional Array (3-D)

Ek array jo multiple 2D arrays store karta hai.

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🔶 Array ke Operations

1. Traversal (Saare Elements ko Ek-ek karke Access Karna)

c

for(int i=0; i<5; i++) {
   cout << arr[i];
}

• Linear Traversal: Start se end tak

• Reverse Traversal: End se start tak

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2. Insertion (Naya Element Add Karna)

• Kisi index pe insert karna ho to baaki elements ko right shift karna padta hai.

• End me insert karna easiest hota hai (agar space ho to).

Example:

c

arr = [10, 20, 30, 40]
Insert 25 at index 2 → arr = [10, 20, 25, 30, 40]

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3. Deletion (Element Remove Karna)

• Kisi index se element delete karna hai to uske baad ke elements ko left shift karna padta hai.

Example:

c

arr = [10, 20, 30, 40]
Delete 30 → arr = [10, 20, 40]

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4. Searching (Element Dhoondhna)

✅ Linear Search

• Saare elements ko ek-ek karke check karo.

• Sorted ya Unsorted array dono mein kaam karta hai.

c

for(int i=0; i<n; i++) {
   if(arr[i] == x) return i;
}

✅ Binary Search

• Sirf sorted array mein kaam karta hai.

• Mid se start karke left ya right half search karta hai.

c

int low = 0, high = n-1;
while(low <= high) {
   int mid = (low + high)/2;
   if(arr[mid] == x) return mid;
   else if(x < arr[mid]) high = mid - 1;
   else low = mid + 1;
}