CTCI 6.08: EggDrop.groovy

src/main/groovy/Ch06_MathAndLogicPuzzles/_06_08_EggDrop.groovy

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+package Ch06_MathAndLogicPuzzles
+
+import static java.lang.Math.max
+import static java.lang.Math.sqrt
+
+/** You are given two identical eggs to find out from which floor of a tall building they would break */
+class _06_08_EggDrop {
+    static dropCount(int floorCount, Closure<Boolean> breaks) {
+        def increment = max(2, (sqrt(1 + 8 * floorCount) - 1) / 2) // x * (x + 1) / 2 = floorCount 
+        def floor = increment
+        while (floor < floorCount && !breaks(floor as int))
+            floor += --increment
+
+        floor = (floor - increment + 1) as int
+        while (floor <= floorCount && !breaks(floor))
+            floor++
+
+        (floor > floorCount) ? Integer.MAX_VALUE
+                             : floor
+    }
+}

src/test/groovy/Ch06_MathAndLogicPuzzles/_06_08_EggDropTest.groovy

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+package Ch06_MathAndLogicPuzzles
+
+import spock.lang.Specification
+
+import static Ch06_MathAndLogicPuzzles._06_08_EggDrop.dropCount
+
+class _06_08_EggDropTest extends Specification {
+    /*@formatter:off*/
+    def 'eggDrop?'() {
+        expect:  for (floorCount in 1..100) {
+                    assert dropCount(floorCount) { false } == Integer.MAX_VALUE 
+                    for (breakingFloor in 1..floorCount)
+                        assert dropCount(floorCount) { it >= breakingFloor } == breakingFloor 
+                }
+    }
+    /*@formatter:on*/
+}