Adding solution for Medium-SplashArrays

Prakhar Gupta · Prakhar Gupta · commit ab5d099a6b6d · 2020-06-03T02:22:03.000-07:00
diff --git a/src/hackerrank/medium/Prakhar_SplashArrays.java b/src/hackerrank/medium/Prakhar_SplashArrays.java
@@ -0,0 +1,36 @@
+import java.util.Arrays;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class Prakhar_SplashArrays {
+
+    /**
+     * Instead of iterating, This approach creates a map of strings to occurence.
+     * The map approach can be implemented from scratch by iterating and iterating the count, or leverage the existing groupBy provided by java8. I chose to do the later.
+     * Once map is created, Its easy to look up.
+     *
+     * Complexity : O(n)
+     */
+    static int[] matchingStrings(final String[] strings, final String[] queries) {
+
+        // Create a Map of each string to its occurence
+        final Map<String, Long> stringToCountMap =
+                Stream.of(strings).collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
+        // Get the result off the map
+        return Arrays.stream(queries)
+                .map(query -> stringToCountMap.getOrDefault(query, 0L))
+                .mapToInt(Math::toIntExact).toArray();
+    }
+
+    public static void main(String[] args) {
+
+        final String[] strings = {"aba", "baba", "aba", "xzxb"};
+        final String[] queries = {"aba", "xzxb", "ab"};
+
+        final int[] output = matchingStrings(strings, queries);
+
+        Arrays.stream(output).forEach(System.out::println);
+    }
+}
