Mastering Simple Nested Loops in Kotlin

Hello there, budding programmer! Are you ready for another fun-filled Kotlin adventure? Today, we're going to dive into the world of nested loops.

Nested loops are a crucial way to perform an action or a group of actions repeatedly. What differentiates them from regular loops is that we can have loops inside other loops!

Our goal for today is to master simple nested loops in Kotlin. We'll start by understanding the basic syntax and control flow, progress into nested for and while loops, and conclude with some common pitfalls to avoid when using nested loops.

Before venturing into nested loops, let's briefly revisit for and while loops.

A for loop in Kotlin iterates over anything that provides an iterator:

for (i in 1..5) {
    println(i) // This will print the numbers 1 to 5
}

A while loop executes a block of code repeatedly as long as a given condition is true:

var count = 1
while (count <= 5) {
    println(count) // This will also print the numbers 1 to 5
    count += 1
}

Having brushed up on for and while loops, we can delve further into the concept of nested loops. Simply put, a nested loop is a loop within another loop. During each iteration of the outer loop, the inner loop completes its entire set of iterations. Here's a basic nested loop in Kotlin:

for (outer in 1..2) {
    for (inner in 1..3) {
        println("Outer:$outer Inner:$inner")
    }
}

/*
The code above has the following output
"""
Outer:1 Inner:1
Outer:1 Inner:2
Outer:1 Inner:3
Outer:2 Inner:1
Outer:2 Inner:2
Outer:2 Inner:3
"""
*/

Nested for loops execute all of their iterations within each iteration of the outer loop, making them useful for handling tasks like processing two-dimensional arrays.

for (row in 1..3) {
    for (col in 1..4) {
        print("* ")
    }
    println() // goes to next line after each row
}

/*
The code above has the following output
"""
* * * * 
* * * * 
* * * * 
"""
*/