/*
Alphabet Rangoli Generator in Kotlin
This program constructs a geometric alphabet pattern of size N.
It uses small helper functions, clear logic, and Kotlin's built‑in
collection operations to keep the implementation concise and efficient.
*/
fun main() {
val n = 5
println(makeRangoli(n))
}
/*
Builds the entire rangoli as a multi-line string.
The pattern is symmetric vertically, so we iterate from -(n-1) to +(n-1).
*/
fun makeRangoli(n: Int): String {
if (n <= 0) return ""
val totalWidth = 4 * n - 3 // Width formula identical to the reference implementation
// Build each row and join them with newline characters
return (-(n - 1)..(n - 1))
.joinToString("\n") { offset ->
buildRow(n, kotlin.math.abs(offset), totalWidth)
}
}
/*
Builds a single row of the rangoli.
currentDist = distance from the center row.
totalWidth = final width after padding with hyphens.
*/
fun buildRow(n: Int, currentDist: Int, totalWidth: Int): String {
// Number of descending characters (e.g., e d c ...)
val count = n - currentDist
// Descending characters: e d c b a (for n=5)
val descending = (0 until count).map { j ->
('a' + (n - 1 - j))
}
// Ascending characters: b c d e (excluding the center)
val ascending = (0 until count - 1).map { j ->
('a' + (n - 1 - j))
}.reversed()
// Combine both sides and insert hyphens
val row = (descending + ascending).joinToString("-")
// Compute padding to center the row
val padding = (totalWidth - row.length) / 2
val hyphens = "-".repeat(padding)
return hyphens + row + hyphens
}
/*
run:
--------e--------
------e-d-e------
----e-d-c-d-e----
--e-d-c-b-c-d-e--
e-d-c-b-a-b-c-d-e
--e-d-c-b-c-d-e--
----e-d-c-d-e----
------e-d-e------
--------e--------
*/
