Kotlin Program: Print Pascal's Triangle for a given number of rows

Kotlin Control Flow: Exercise-5 with Solution

Write a Kotlin program to print the Pascal's triangle of a given number of rows.

Sample Solution:

Kotlin Code:

fun printPascalTriangle(rows: Int) {
    require(rows > 0) { "Number of rows must be greater than 0." }

    var prevRow = mutableListOf(1)
    println(prevRow.joinToString(" "))

    for (currentRow in 1 until rows) {
        val nextRow = mutableListOf()

        nextRow.add(1)
        for (i in 1 until currentRow) {
            val sum = prevRow[i - 1] + prevRow[i]
            nextRow.add(sum)
        }
        nextRow.add(1)

        println(nextRow.joinToString(" "))

        prevRow = nextRow
    }
}

fun main() {
    val numRows = 7
    printPascalTriangle(numRows)
} 

Sample Output:

1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1
1 6 15 20 15 6 1

Explanation:

In the above exercise,

• The "printPascalTriangle()" function takes the rows parameter, which specifies the number of rows to be printed in Pascal's triangle. It first checks if the number of rows is greater than 0 using the require function.
• The program then initializes prevRow as a mutable list containing the first row with a single element, which is always 1. This row is printed using the "println()" and "joinToString()" functions to concatenate the row elements with spaces.
• The program then enters a loop to calculate and print the subsequent rows. It initializes an empty mutable list nextRow. It adds 1 as the first element of the row, and then calculates the remaining elements by summing the corresponding elements from the previous row (prevRow). The calculated elements are added to nextRow.
• Finally, the nextRow is printed, and prevRow is updated to nextRow for the next iteration. The loop continues until the desired number of rows is printed.
• In the "main()" function, a sample value of numRows (7) is provided, and printPascalTriangle is called with this value. The program then prints Pascal's triangle with7 rows.

Kotlin Editor:

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