Arrays in C++

C++ mein jab humein multiple same-type variables ko store karna hota hai, tab Array ka use kiya jaata hai. Arrays programming ka ek basic but super useful concept hai, especially jab aapko large amount of data ke saath kaam karna ho.

• Array kya hota hai?
• Declaration, Initialization, and Access
• Input and Output in Arrays
• Array traversal
• Basic problems like sum, max, reverse
• Limitations of arrays

1. Array Kya Hota Hai?

Array ek aisa data structure hai jisme aap ek hi type ke multiple elements ko ek sath store kar sakte ho — aur sabhi elements memory mein continuous location pe store hote hain.

Think of it like: Ek train ke dibbe jisme sab log same class ke hain (e.g., sleeper).

int numbers[5];  // Ek array jo 5 integers store kar sakta hai

2. Array Declaration and Initialization

Declaration:

int arr[5];   // 5 size ka integer array
float prices[10]; // 10 float values store hongi

Initialization:

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

Agar aap initialize karte ho to size dena optional hai:

int arr[] = {1, 2, 3};

3. Accessing Elements (Indexing)

Array elements ko access karne ke liye indexing use hoti hai. Index 0 se start hota hai.

cout << arr[0];  // First element
cout << arr[4];  // Fifth element

Agar aap out-of-bound index (jaise arr[5] in a 5-size array) access karoge, to undefined behavior ho sakta hai ⚠️

4. Input and Output in Arrays

Input from User:

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

Output:

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

5. Common Array Programs

1. Sum of Array Elements:

#include<iostream>
using namespace std;
int main(){
int arr[5] = {1, 2, 3, 4, 5};
int sum = 0;

for (int i = 0; i < 5; i++) {
    sum += arr[i];
}
cout << "Sum: " << sum;
return 0;
}

Output:

Sum: 15

2. Maximum Element in Array

#include<iostream>
using namespace std;
int main(){
int arr[] = {4, 9, 10, 8, 1};
int max = arr[0];
for (int i = 1; i < 5; i++) {
    if (arr[i] > max)
        max = arr[i];
}
cout << "Max element: " << max;
return 0;
}

Output:

Max element: 1

3. Reverse Array

#include<iostream>
using namespace std;
int main(){
int arr[] = {4, 9, 10, 8, 1};
for (int i = 4; i >= 0; i--) {
    cout << arr[i] << ", ";
}
return 0;
}

Output:

1, 8, 10, 9, 4

6. Two Dimensional Arrays

2D arrays ka use tab hota hai jab aapko rows & columns ke format mein data store karna ho (e.g., matrix).

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

Access:

cout << matrix[1][2]; // Output: 6

Matrix Printing Program:

#include<iostream>
using namespace std;
int main(){
int matrix[2][3] = {
  {1, 2, 3},
  {4, 5, 6}
};
cout<<"Matrix"<<endl;
for(int i = 0; i < 2; i++){
   for(int j = 0; j < 3; j++){
      cout<<matrix[i][j]<<" ";
     }
   cout<<endl;
 }
return 0;
}

Array Ki Limitations

• Fixed size hota hai (static memory allocation)
• Run-time pe size change nahi ho sakta
• No built-in bounds checking (error nahi aata agar galat index access ho)

Practice Questions

1. Ek array lo jisme user se 10 numbers input le aur unka average print karo.
2. Ek program likho jo array ka minimum element dhoondhe.
3. Ek 2D array banao aur uska transpose nikaalo.
4. Ek array reverse karo bina second array use kiye (in-place reverse).