updated

Author: bhishma620

src/main/java/com/thealgorithms/dynamicprogramming/Sum_Of_Subset.java

@@ -1,29 +1,41 @@
-package com.thealgorithms.dynamicprogramming;
+package com.example.algo;
 
 public class Sum_Of_Subset {
 
     public static void main(String[] args) {
         int[] arr = {7, 3, 2, 5, 8};
         int Key = 14;
 
-        if (subsetSum(arr, arr.length - 1, Key)) {
+        if (subsetSum(arr, arr.length, Key)) {
             System.out.print("Yes, that sum exists");
         } else {
             System.out.print("Nope, that number does not exist");
         }
     }
 
-    public static boolean subsetSum(int[] arr, int num, int Key) {
-        if (Key == 0) {
-            return true;
-        }
-        if (num < 0 || Key < 0) {
-            return false;
+    static boolean subsetSum(int[] arr, int n, int Key) {
+        boolean[] prev = new boolean[Key + 1];
+
+        prev[0] = true;
+
+        if (arr[0] <= Key) {
+            prev[arr[0]] = true;
         }
 
-        boolean include = subsetSum(arr, num - 1, Key - arr[num]);
-        boolean exclude = subsetSum(arr, num - 1, Key);
+        for (int ind = 1; ind < n; ind++) {
+            boolean[] cur = new boolean[Key + 1];
+            cur[0] = true;
+            for (int target = 1; target <= Key; target++) {
+                boolean notTaken = prev[target];
+                boolean taken = false;
+                if (arr[ind] <= target) {
+                    taken = prev[target - arr[ind]];
+                }
+                cur[target] = notTaken || taken;
+            }
+            prev = cur;
+        }
 
-        return include || exclude;
+        return prev[Key];
     }
 }

src/test/java/com/thealgorithms/sorts/Sum_Of_SubSetTest.java

@@ -0,0 +1,21 @@
+package com.thealgorithms.sorts;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class Sum_Of_SubsetTest {
+
+    @Test
+    void basicCheck() {
+        assertEquals(true, Sum_Of_Subset.subsetSum(new int[] {7, 3, 2, 5, 8}, 5, 14));
+
+        assertEquals(true, Sum_Of_Subset.subsetSum(new int[] {4, 3, 2, 1}, 4, 5));
+
+        assertEquals(false, Sum_Of_Subset.subsetSum(new int[] {2, 5, 1, 6, 7}, 5, 4));
+
+        assertEquals(false, Sum_Of_Subset.subsetSum(new int[] {1, 7, 2, 9, 10}, 5, 14));
+
+        assertEquals(true, Sum_Of_Subset.subsetSum(new int[] {1, 7, 2, 9, 10}, 5, 13));
+    }
+}