Created SubsetSum.java

DynamicProgramming/SubsetSum.java

@@ -0,0 +1,57 @@
+package DynamicProgramming;
+
+public class SubsetSum {
+
+    /*
+    This algorithm will determine if a set of integers contains
+    a subset that sum to a given integer. The algorithm will
+    return true if such a subset exists and false otherwise.
+    This is a dynamic programming implementation.
+     */
+
+    private static boolean subsetSum(int arr[], int n, int sum){
+        boolean isSum[][] = new boolean[n + 2][sum + 1];
+
+        isSum[n + 1][0] = true;
+        for (int i = 1; i <= sum; i++) {
+            isSum[n + 1][i] = false;
+        }
+
+        for (int i = n; i > 0; i--) {
+            isSum[i][0] = true;
+            for (int j = 1; j <= arr[i - 1] - 1; j++) {
+                if (j <= sum) {
+                    isSum[i][j] = isSum[i + 1][j];
+                }
+            }
+            for (int j = arr[i - 1]; j <= sum; j++) {
+                isSum[i][j] = (isSum[i + 1][j] || isSum[i + 1][j - arr[i - 1]]);
+            }
+        }
+
+        return isSum[1][sum];
+    }
+
+    /*
+    This is a driver method to run the algorithm with four
+    test values: the first two should evaluate true, and the
+    last two should evaluate false.
+     */
+    public static void main(String args[]) {
+        int arr[] = new int[]{50, 4, 10, 15, 34};
+        int n = arr.length;
+        // 4 + 10 + 15 + 34 = 64
+        int sum1 = 64;
+        // 50 + 15 + 34 = 99
+        int sum2 = 99;
+        // No subset of the given array will give a sum
+        //  of 5 or 66
+        int sum3 = 5;
+        int sum4 = 66;
+
+        System.out.println(subsetSum(arr, n, sum1));
+        System.out.println(subsetSum(arr, n, sum2));
+        System.out.println(subsetSum(arr, n, sum3));
+        System.out.println(subsetSum(arr, n, sum4));
+    }
+}