Added thomas algorithm in kotlin (algorithm-archivists#539)

Author: sklan

contents/thomas_algorithm/code/kotlin/thomas.kt

@@ -0,0 +1,33 @@
+private fun thomas(a: DoubleArray, b: DoubleArray, c: DoubleArray, d: DoubleArray): DoubleArray {
+    val cPrime = c.clone()
+    val x = d.clone()
+    val size = a.size
+    cPrime[0] /= b[0]
+    x[0] /= b[0]
+    for (i in 1 until size) {
+        val scale = 1.0 / (b[i] - cPrime[i - 1] * a[i])
+        cPrime[i] *= scale
+        x[i] = (x[i] - a[i] * x[i - 1]) * scale
+    }
+    for (i in (size - 2) downTo 0) {
+        x[i] -= cPrime[i] * x[i + 1]
+    }
+    return x
+}
+
+fun main(args: Array<String>) {
+    val a = doubleArrayOf(0.0, 2.0, 3.0)
+    val b = doubleArrayOf(1.0, 3.0, 6.0)
+    val c = doubleArrayOf(4.0, 5.0, 0.0)
+    val x = doubleArrayOf(7.0, 5.0, 3.0)
+    val solution = thomas(a, b, c, x)
+
+    println("System:")
+    println("[%.1f, %.1f, %.1f][x] = [%.1f]".format(b[0], c[0], 0f, x[0]))
+    println("[%.1f, %.1f, %.1f][y] = [%.1f]".format(a[1], b[1], c[1], x[1]))
+    println("[%.1f, %.1f, %.1f][z] = [%.1f]\n".format(0f, a[2], b[2], x[2]))
+    println("Solution:")
+    for (i in solution.indices) {
+        println("[% .5f]".format(solution[i]))
+    }
+}

contents/thomas_algorithm/thomas_algorithm.md

@@ -125,6 +125,8 @@ You will find this algorithm implemented [in this project](https://scratch.mit.e
 [import, lang:"lua"](code/lua/thomas.lua)
 {% sample lang="crystal" %}
 [import, lang:"crystal"](code/crystal/thomas.cr)
+{% sample lang="kotlin" %}
+[import, lang:"kotlin"](code/kotlin/thomas.kt)
 {% endmethod %}
 
 <script>