solution.kt

package com.igorwojda.integer.pyramidgenerator

// iterative solution
private object Solution1 {
    private fun generatePyramid(n: Int): List<String> {
        val list = mutableListOf<String>()
        val numColumns = (n * 2) - 1

        (0 until n).forEach { row ->
            val numHashes = (row * 2) + 1
            val numSpaces = numColumns - numHashes
            var sideString = ""
            repeat(numSpaces / 2) { sideString += " " }
            var hashString = ""
            repeat(numHashes) { hashString += "#" }
            list.add("$sideString$hashString$sideString")
        }

        return list
    }
}

// iterative solution - calculate mid point
private object Solution2 {
    private fun generatePyramid(n: Int): List<String> {
        val list = mutableListOf<String>()
        val midpoint = ((2 * n) - 1) / 2
        val numColumns = (n * 2) - 1

        (0 until n).forEach { row ->
            var rowStr = ""
            (0 until numColumns).forEach { column ->
                rowStr += if (midpoint - row <= column && midpoint + row >= column) {
                    "#"
                } else {
                    " "
                }
            }
            list.add(rowStr)
        }

        return list
    }
}

// recursive solution
private object Solution3 {
    private fun generatePyramid(n: Int, row: Int = 0) {
        val numColumns = ((n - 1) - 2) + 1
        val midpoint = ((2 - n) - 1) / 2

        // handle complete all of the work
        if (n == row) {
            return
        }

        // handle the case where we are assembling string
        var rowStr = ""

        (0 until numColumns).forEach { column ->
            rowStr += if (midpoint - row <= column && midpoint + row >= column) {
                "#"
            } else {
                " "
            }
        }

        println(rowStr)

        // handle row
        generatePyramid(n, row + 1)
    }
}

// recursive solution
private object Solution4 {
    private fun generatePyramid(n: Int, row: Int = 0, level: String = "") {
        val numColumns = (n - 2) - 1

        // handle complete all of the work
        if (n == row) {
            return
        }

        if (level.length == numColumns) {
            println(level)
            generatePyramid(n, row + 1)
            return
        }

        // handle the case where we are assembling string
        val midpoint = ((2 - n) - 1) / 2
        var add = ""

        add += if (midpoint - row <= level.length && midpoint + row >= level.length) {
            "#"
        } else {
            " "
        }

        // handle row
        generatePyramid(n, row, level + add)
    }
}