Two Sum

ardallie · ardallie · commit ffe2fad476e0 · 2021-08-16T22:32:29.000+01:00
diff --git a/src/easy/TwoSum.java b/src/easy/TwoSum.java
@@ -0,0 +1,50 @@
+package easy;
+
+/**
+ * Have the function TwoSum(arr) take the array of integers stored in arr,
+ * and determine if any two numbers (excluding the first element)
+ * in the array can sum up to the first element in the array.
+ * ---
+ * For example: if arr is [7, 3, 5, 2, -4, 8, 11],
+ * then there are actually two pairs that sum to the number 7: [5, 2] and [-4, 11].
+ * ---
+ * Your program should return all pairs,
+ * with the numbers separated by a comma,
+ * in the order the first number appears in the array.
+ * Pairs should be separated by a space.
+ * So for the example above, your program would return: 5,2 -4,11
+ */
+public class TwoSum {
+
+  /**
+   * Two Sum function.
+   *
+   * @param arr input array
+   * @return all pairs
+   */
+  private static String twoSum(int[] arr) {
+    StringBuilder output = new StringBuilder();
+    for (int i = 1; i < arr.length; i++) {
+      for (int j = i + 1; j < arr.length; j++) {
+        if (arr[i] + arr[j] == arr[0]) {
+          if (output.length() > 0) {
+            output.append(" ");
+          }
+          output.append(arr[i]).append(",").append(arr[j]);
+        }
+      }
+    }
+    return output.length() == 0 ? "-1" : output.toString();
+  }
+
+  /**
+   * Entry point.
+   *
+   * @param args command line arguments
+   */
+  public static void main(String[] args) {
+    var result = twoSum(new int[]{8, 1, 2, 3, 4, 5, 7});
+    System.out.println(result);
+  }
+
+}
