for Loop in C++

 

The for loop in C++ is one of the most commonly used loops to repeat a block of code a specific number of times. It's ideal when you know in advance how many times you want to execute a block of code.

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1️⃣ Syntax of for Loop:

for (initialization; condition; increment/decrement) {
    // Code to be executed
}

• initialization: This step is executed only once, before the loop starts. It's typically used to set the loop control variable.
• condition: This expression is evaluated before each iteration. If the condition is true, the loop continues; otherwise, it exits.
• increment/decrement: This step is executed after each iteration. It's used to update the loop control variable.

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2️⃣ Example: Basic for Loop

Here’s a simple example that prints numbers from 1 to 5 using a for loop:

#include <iostream>
using namespace std;

int main() {
    // for loop to print numbers 1 to 5
    for (int i = 1; i <= 5; i++) {
        cout << i << " ";
    }
    return 0;
}

Explanation:

• Initialization: int i = 1 (start at 1)
• Condition: i <= 5 (continue as long as i is less than or equal to 5)
• Increment: i++ (increase i by 1 after each iteration)

Output:

1 2 3 4 5

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3️⃣ Example: for Loop with Decrement

You can also use the for loop to count downwards. Here's an example where we print numbers from 5 to 1:

#include <iostream>
using namespace std;

int main() {
    // for loop to print numbers 5 to 1
    for (int i = 5; i >= 1; i--) {
        cout << i << " ";
    }
    return 0;
}

Explanation:

• Initialization: int i = 5 (start at 5)
• Condition: i >= 1 (continue as long as i is greater than or equal to 1)
• Decrement: i-- (decrease i by 1 after each iteration)

Output:

5 4 3 2 1

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4️⃣ Example: Nested for Loop

A nested for loop is a for loop inside another for loop. It's useful when you need to perform multiple iterations for each iteration of the outer loop. Here's an example that prints a multiplication table:

#include <iostream>
using namespace std;

int main() {
    int rows = 5;
    
    // Nested for loop for multiplication table
    for (int i = 1; i <= rows; i++) {
        for (int j = 1; j <= rows; j++) {
            cout << i * j << "\t";  // Print the product
        }
        cout << endl;  // Move to the next line after each row
    }

    return 0;
}

Explanation:

• The outer loop runs from 1 to 5 (the number of rows).
• The inner loop runs from 1 to 5 for each iteration of the outer loop, printing the product of i and j.

Output:

1	2	3	4	5	
2	4	6	8	10	
3	6	9	12	15	
4	8	12	16	20	
5	10	15	20	25

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5️⃣ Example: for Loop with Multiple Initialization or Increment

You can have multiple initialization and increment expressions in a for loop. Here's an example where we initialize multiple variables and update them in the loop:

#include <iostream>
using namespace std;

int main() {
    // Multiple initialization and increment in for loop
    for (int i = 1, j = 10; i <= 5; i++, j--) {
        cout << "i: " << i << ", j: " << j << endl;
    }
    return 0;
}

Explanation:

• Initialization: int i = 1, j = 10 (initialize two variables i and j)
• Condition: i <= 5 (loop continues until i reaches 5)
• Increment/Decrement: i++ and j-- (increase i and decrease j after each iteration)

Output:

i: 1, j: 10
i: 2, j: 9
i: 3, j: 8
i: 4, j: 7
i: 5, j: 6

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6️⃣ Example: for Loop with continue and break

• continue: Skips the rest of the loop's body for the current iteration and moves to the next iteration.
• break: Exits the loop entirely, even if the condition hasn't been met.

Here’s an example using both continue and break:

#include <iostream>
using namespace std;

int main() {
    // for loop with continue and break
    for (int i = 1; i <= 10; i++) {
        if (i == 5) {
            continue;  // Skip the iteration when i is 5
        }
        if (i == 8) {
            break;  // Exit the loop when i is 8
        }
        cout << i << " ";
    }

    return 0;
}

Explanation:

• The loop will skip the number 5 because of the continue statement.
• The loop will terminate when i is 8 due to the break statement.

Output:

1 2 3 4 6 7

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7️⃣ Key Points to Remember:

• Initialization: Typically done at the beginning of the for loop.
• Condition: Checked before each iteration.
• Increment/Decrement: Used to update the loop variable (e.g., i++ or i--).
• Nested Loops: Useful for multi-dimensional problems, like matrices or grids.
• Control Statements: continue skips the current iteration, while break exits the loop.

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Would you like to explore any specific use cases for the for loop, like processing arrays or strings, or would you prefer to dive deeper into more advanced loops?