C++ for Loop

🔁 C++ for Loop

for loop ka use tab hota hai jab pehle se pata ho loop kitni baar chalega.
Ye initialization, condition, increment/decrement ko ek hi line mein likhne deta hai.

🔹 1. Syntax

for (initialization; condition; update) {
// code
}

  • Initialization → loop start

  • Condition → true tak loop chale

  • Update → har iteration ke baad change

🔹 2. Basic Example (1 to 5)

for (int i = 1; i <= 5; i++) {
cout << i << " ";
}

Output:

1 2 3 4 5

🔹 3. Print Even Numbers

for (int i = 2; i <= 10; i += 2) {
cout << i << " ";
}

🔹 4. Reverse Loop (5 to 1)

for (int i = 5; i >= 1; i--) {
cout << i << " ";
}

🔹 5. Sum of Numbers (1 to 10)

int sum = 0;

for (int i = 1; i <= 10; i++) {
sum += i;
}

cout << sum;

🔹 6. Nested for Loop

for (int i = 1; i <= 3; i++) {
for (int j = 1; j <= 3; j++) {
cout << i << j << " ";
}
}

Output:

11 12 13 21 22 23 31 32 33

🔹 7. Loop Without Initialization / Update

int i = 1;

for (; i <= 5; ) {
cout << i << " ";
i++;
}

🔹 8. Range-Based for Loop (Modern C++)

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

for (int x : arr) {
cout << x << " ";
}

❌ Common Mistakes

for (int i = 1; i <= 5; i++); // ❌ extra semicolon
{
cout << i;
}

📌 Summary

  • for loop jab iterations known ho

  • Clean & compact syntax

  • Supports nested loops

  • Range-based loop best for arrays

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