Introduction to C++ | for Loop

C++ for Loop

The for loop in C++ is a control structure that allows you to repeat a block of code a certain number of times. It's commonly used when the number of iterations is known beforehand. It is very useful when you need to perform repetitive tasks such as iterating over arrays, ranges, or performing operations on numbers.

What is a for Loop?

The for loop consists of three parts:

Syntax:

Syntax of a for Loop


        for (initialization; condition; increment/decrement) {
            // code to be executed on each iteration
        }

Example of for Loop

Here’s an example where a for loop is used to print the numbers from 1 to 5:

Code Example


        #include <iostream>
        using namespace std;
        
        int main() {
            // for loop to print numbers from 1 to 5
            for (int i = 1; i <= 5; i++) {
                cout << "Number: " << i << endl;
            }
        
            return 0;
        }

Output

Number: 1
Number: 2
Number: 3
Number: 4
Number: 5

Nested for Loops

In some cases, you might need to use multiple loops. A nested for loop is a loop inside another loop. This is useful for tasks such as iterating over multi-dimensional arrays or performing tasks with multiple variables.

Example of a nested for loop:

Code Example: Nested for Loops


        #include <iostream>
        using namespace std;
        
        int main() {
            // Nested for loop to print a multiplication table
            for (int i = 1; i <= 5; i++) {
                for (int j = 1; j <= 5; j++) {
                    cout << i * j << "t";  // Multiplying i and j
                }
                cout << endl;  // Move to the next line after each row
            }
        
            return 0;
        }

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

Break and Continue in for Loop

You can also control the flow of a for loop using break and continue. The break statement immediately exits the loop, while the continue statement skips the current iteration and moves to the next one.

Example of using break and continue in a for loop:

Code Example with break and continue


        #include <iostream>
        using namespace std;
        
        int main() {
            // for loop with break and continue
            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 = " << i << endl;
            }
        
            return 0;
        }

Output

i = 1
i = 2
i = 3
i = 4
i = 6
i = 7

Pro Tip:

💡 Pro Tip

For loops are particularly useful when the number of iterations is known in advance. When using nested loops, be careful about performance, as the time complexity increases exponentially with the number of nested loops. If performance is a concern, consider optimizing your algorithm or using other loop structures, such as while loops or do-while loops.