Three Sum

ardallie · ardallie · commit 207a1091e969 · 2021-08-16T22:09:04.000+01:00
diff --git a/src/easy/ThreeSum.java b/src/easy/ThreeSum.java
@@ -0,0 +1,48 @@
+package easy;
+
+/**
+ * Have the function ThreeSum(arr) take the array of integers stored in arr,
+ * and determine if any three distinct numbers (excluding the first element)
+ * in the array can sum up to the first element in the array.
+ * ---
+ * For example: if arr is [8, 2, 1, 4, 10, 5, -1, -1] then
+ * there are actually three sets of triplets
+ * that sum to the number 8: [2, 1, 5], [4, 5, -1] and [10, -1, -1].
+ * ---
+ * Your program should return the string true
+ * if 3 distinct elements sum to the first element,
+ * otherwise your program should return the string false.
+ * The input array will always contain at least 4 elements.
+ */
+public class ThreeSum {
+
+  /**
+   * Three Sum function.
+   *
+   * @param arr input array
+   * @return "true" if 3 distinct elements sum to the first element
+   */
+  private static String threeSum(int[] arr) {
+    for (int i = 1; i < arr.length; i++) {
+      for (int j = i + 1; j < arr.length; j++) {
+        for (int k = j + 1; k < arr.length; k++) {
+          if (arr[i] + arr[j] + arr[k] == arr[0]) {
+            return "true";
+          }
+        }
+      }
+    }
+    return "false";
+  }
+
+  /**
+   * Entry point.
+   *
+   * @param args command line arguments
+   */
+  public static void main(String[] args) {
+    var result = threeSum(new int[]{8, 1, 2, 3, 4, 5, 7});
+    System.out.println(result);
+  }
+
+}
