[hackerrank] Common Child

Author: codehumane

src/main/kotlin/hackerrank/string/CommonChild.kt

@@ -0,0 +1,52 @@
+package hackerrank.string
+
+import kotlin.math.max
+
+/**
+ * AA, BB
+ * HARRY, SALLY
+ * SHINCHAN, NOHARAAA
+ * ABCDEF, FBDAMN
+ *
+ *   SHINCHAHN
+ * N 000111111
+ * O -
+ * H 011111111
+ * H 011112222
+ * A 011112333
+ * R -
+ * A -
+ * A -
+ * A -
+ *
+ */
+fun commonChild(s1: String, s2: String): Int {
+    val counts = Array(s1.length + 1) { IntArray(s2.length + 1) }
+
+    s1.forEachIndexed { i1, c1 ->
+        s2.forEachIndexed { i2, c2 ->
+            counts[i1 + 1][i2 + 1] = if (c1 == c2) {
+                counts[i1][i2] + 1
+            } else {
+                max(counts[i1 + 1][i2], counts[i1][i2 + 1])
+            }
+        }
+
+        printMatrix(counts, s1, s2)
+    }
+
+    return counts[s1.length][s2.length]
+}
+
+private fun printMatrix(counts: Array<IntArray>, s1: String, s2: String) {
+    val s2Joined = s2.toCharArray().joinToString(" ")
+
+    var s1CharIndex = 0
+    val joined = counts
+        .filterIndexed { i, _ -> i > 0 }
+        .joinToString("\n") {
+            "${s1[s1CharIndex++]} ${it.filterIndexed { i, _ -> i > 0 }.joinToString(" ")}"
+        }
+
+    println("matrix is...\n  $s2Joined\n$joined")
+}

src/test/kotlin/hackerrank/string/CommonChildKtTest.kt

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+package hackerrank.string
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class CommonChildKtTest {
+
+    @Test
+    fun commonChild() {
+        assertEquals(0, commonChild("AA", "BB"))
+        assertEquals(2, commonChild("HARRY", "SALLY"))
+        assertEquals(3, commonChild("SHINCHAN", "NOHARAAA"))
+        assertEquals(2, commonChild("ABCDEF", "FBDAMN"))
+    }
+
+}