Added array pair sum exercise.

stringbasic · stringbasic · commit 7eddabc343ff · 2020-01-04T19:45:37.000Z
diff --git a/src/main/java/stringbasic/exercises/ArrayPairSum.java b/src/main/java/stringbasic/exercises/ArrayPairSum.java
@@ -0,0 +1,32 @@
+package stringbasic.exercises;
+
+import java.util.ArrayList;
+
+/**
+ * Finds pair in an array which sum equals to a given value
+ */
+public class ArrayPairSum<T> {
+
+    private int sum;
+
+    /**
+     *
+     * @param sum sum value to look for
+     */
+    public ArrayPairSum(int sum) {
+        this.sum = sum;
+    }
+
+    public Pair[] getPairs(int[] elements) {
+        ArrayList<Pair> results = new ArrayList<Pair>();
+        for (int i = 0; i < elements.length; i++) {
+            for (int j = i+1; j < elements.length; j++) {
+                if (elements[i] + elements[j] == this.sum) {
+                    results.add(new Pair(elements[i], elements[j]));
+                }
+            }
+        }
+
+        return results.toArray(new Pair[0]);
+    }
+}
diff --git a/src/main/java/stringbasic/exercises/Pair.java b/src/main/java/stringbasic/exercises/Pair.java
@@ -0,0 +1,51 @@
+package stringbasic.exercises;
+
+import java.util.Objects;
+
+/**
+ * Pair container for int elements
+ */
+public class Pair {
+
+    private int first;
+    private int second;
+
+    public Pair() {
+
+    }
+
+    public Pair(int first, int second) {
+        this.first = first;
+        this.second = second;
+    }
+
+    public int getFirst() {
+        return first;
+    }
+
+    public void setFirst(int first) {
+        this.first = first;
+    }
+
+    public int getSecond() {
+        return second;
+    }
+
+    public void setSecond(int second) {
+        this.second = second;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Pair pair = (Pair) o;
+        return getFirst() == pair.getFirst() &&
+                getSecond() == pair.getSecond();
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(getFirst(), getSecond());
+    }
+}
diff --git a/src/test/java/stringbasic/exercises/ArrayPairSumTest.java b/src/test/java/stringbasic/exercises/ArrayPairSumTest.java
@@ -0,0 +1,39 @@
+package stringbasic.exercises;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertArrayEquals;
+
+public class ArrayPairSumTest {
+    @Test
+    public void testGetPairsEmpty() {
+        ArrayPairSum arrayPairSum = new ArrayPairSum(10);
+        Pair[] expected = new Pair[0];
+        int[] emptyArray = {};
+        assertArrayEquals("expecting empty array", expected, arrayPairSum.getPairs(emptyArray));
+    }
+
+    @Test
+    public void testGetPairsOnePair() {
+        ArrayPairSum arrayPairSum = new ArrayPairSum(10);
+        Pair[] expected = new Pair[] {new Pair(3,7)};
+        int[] testArray = {1,6,3,5,7};
+        assertArrayEquals("one pair expected", expected, arrayPairSum.getPairs(testArray));
+    }
+
+    @Test
+    public void testGetPairsMultiplePairs() {
+        ArrayPairSum arrayPairSum = new ArrayPairSum(10);
+        Pair[] expected = new Pair[] {new Pair(3,7), new Pair(6,4), new Pair(5,5)};
+        int[] testArray = {3,1,6,4,5,7,5};
+        assertArrayEquals("one pair expected", expected, arrayPairSum.getPairs(testArray));
+    }
+
+    @Test
+    public void testGetPairsNegativeNumbers() {
+        ArrayPairSum arrayPairSum = new ArrayPairSum(10);
+        Pair[] expected = new Pair[] {new Pair(-3,13), new Pair(24,-14), new Pair(5,5)};
+        int[] testArray = {-3,1,24,-14,5,13,5};
+        assertArrayEquals("one pair expected", expected, arrayPairSum.getPairs(testArray));
+    }
+}
