feat(strings): spreadsheet encoding

buildSrc/src/main/kotlin/Versions.kt

@@ -1,6 +1,6 @@
 object Versions {
     const val PROJECT = "2.1.1"
-    const val KOTLIN = "2.0.21"
+    const val KOTLIN = "2.1.0"
     const val GRADLE = "6.8.3"
 
     const val DETEKT = "1.9.1"

ktstrings/src/main/kotlin/com/kotlinground/strings/spreadsheetencode/README.md

@@ -0,0 +1,5 @@
+# Spreadsheet Encoding
+
+We will be considering how to solve the problem of implementing a function that converts a spreadsheet column ID 
+(i.e., “A”, “B”, “C”, …, “Z”, “AA”, etc.) to the corresponding integer. For example, “A” equals 1 because it represents 
+the first column, while “AA” equals 27 because it represents the 27th column.

ktstrings/src/main/kotlin/com/kotlinground/strings/spreadsheetencode/spreadsheetEncode.kt

@@ -0,0 +1,28 @@
+package com.kotlinground.strings.spreadsheetencode
+import kotlin.math.pow
+
+/**
+ * This encodes a Spreadsheet column ID as an integer and returns it.
+ * Here the encoding uses the alphabets A, B, C, etc. and
+ * further uses the indexing of the alphabet starting from 1 like: A=1, B=2, C=3,..., Z=26
+ * Complexity
+ * Where n represents the number of characters in the column_id
+ *
+ * - Time O(n) as we iterate over each character in the column ID to calculate the encoding
+ * - Space O(1) no extra space is required to perform the encoding
+ * @param columnID [String] column ID to encode, e.g. A or ZZ
+ * @return [Int] the encoded column ID
+ */
+fun spreadsheetEncodeColumn(columnID: String): Int {
+    var num = 0
+    var count = columnID.length - 1
+
+    for (char in columnID) {
+        val diff = char.code - 'A'.code + 1
+        val base = 26.0.pow(count).toInt()
+        num += base * diff
+        count--
+    }
+
+    return num
+}

ktstrings/src/test/kotlin/com/kotlinground/strings/spreadsheetencode/SpreadsheetEncodeTest.kt

@@ -0,0 +1,15 @@
+package com.kotlinground.strings.spreadsheetencode
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class SpreadsheetEncodeTest {
+
+    @Test
+    fun `should return 702 for a column ID of ZZ`() {
+        val columnID = "ZZ"
+        val expected = 702
+        val actual = spreadsheetEncodeColumn(columnID)
+        assertEquals(expected, actual)
+    }
+}