Sum of two

codejayant · codejayant · commit e02cd85edaac · 2021-05-16T13:25:36.000-07:00
diff --git a/src/main/java/com/codejayant/arrays/MaxSubArray.java b/src/main/java/com/codejayant/arrays/MaxSubArray.java
@@ -26,7 +26,9 @@ public static void main(String[] args) {
 
     /**
      * greedy approach
+     * <p>
      * Time complexity : O(N) since it's one pass along the array.
+     * <p>
      * Space complexity : O(1), since it's a constant space solution.
      *
      * @param nums input array
diff --git a/src/main/java/com/codejayant/arrays/SumOfTwo.java b/src/main/java/com/codejayant/arrays/SumOfTwo.java
@@ -0,0 +1,58 @@
+package com.codejayant.arrays;
+
+import org.junit.Assert;
+
+import java.util.HashSet;
+
+/**
+ * For a given two array of integer, find out if there are integers in each array whose sum is equal to a given value.
+ * If yes, return true otherwise false.
+ *
+ * Example:
+ * Input: [1, 2, 3], [10, 20, 30, 40], 42 (value)
+ * Output: true
+ * Explanation: 2 (from first array) + 40 (from second array) = 42
+ */
+public class SumOfTwo {
+
+    public static void main(String[] args) {
+        Integer[] a = {1, 2, 3};
+        Integer[] b = {10, 20, 30, 40};
+
+        Assert.assertTrue(sumOfTwo(a, b, 42));
+        Assert.assertFalse(sumOfTwo(a, b, 45));
+        Assert.assertTrue(sumOfTwo(a, b, 43));
+
+    }
+
+    /**
+     * Calculate compliment from first array, save in a HashSet and check if the element exists by comparing with second array elements.
+     * <p>
+     * Time Complexity: O(n) since there are two sequential loop execution
+     * <p>
+     * Space Complexity: O(n) since a new DS HashSet is introduced saving all complimentary elements from Array first
+     *
+     * @param a first input array
+     * @param b second input array
+     * @param value input sum value
+     * @return true if some element in First Array + some element in Second Array = {@code array}
+     */
+    private static boolean sumOfTwo(Integer[] a, Integer[] b, int value) {
+//        HashSet<Integer> complimentA = Arrays.stream(a)
+//                .map(integer -> value - integer)
+//                .collect(Collectors.toCollection(HashSet::new));
+
+        HashSet<Integer> complimentA = new HashSet<>();
+        for (Integer integer : a) {
+            complimentA.add(value - integer);
+        }
+
+        for (Integer integer : b) {
+            if (complimentA.contains(integer)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+}

Original file line number	Diff line number	Diff line change
`@@ -26,7 +26,9 @@ public static void main(String[] args) {`
`26`	`26`
`27`	`27`	`/**`
`28`	`28`	`* greedy approach`
	`29`	`+ * <p>`
`29`	`30`	`* Time complexity : O(N) since it's one pass along the array.`
	`31`	`+ * <p>`
`30`	`32`	`* Space complexity : O(1), since it's a constant space solution.`
`31`	`33`	`*`
`32`	`34`	`* @param nums input array`