Added backtracking sum of subset

Backtracking/SumOfSubset.js

@@ -0,0 +1,77 @@
+/*
+ *
+ *  Sum of Subset problem
+ *
+ *  Given an ordered set W of non-negative integers and a value K,
+ *  determine all possible subsets from the given set W whose sum
+ *  of its elemets equals to the given value K.
+ *
+ *  More info: https://www.geeksforgeeks.org/subset-sum-backtracking-4/
+ */
+
+/*
+ * @param {number[]} set Original set of numbers
+ * @param {number[]} subset Subset being evaluated
+ * @param {number} setIndex Index from set of last element in subset
+ * @param {number} Sum of elements from subset
+ * @param {targetSum} The target sum on which the subset sum is compared to
+ * @returns {number[][]} Subsets whose elements add up to targetSum
+ */
+const subsetSum = (set, subset, setindex, sum, targetSum) => {
+    // Base case where the subset sum is equal to target sum
+    // Evaluation of following subsets on this path will always add up to
+    // greater than targetSum, so no need to continue
+    if (sum === targetSum) return [subset];
+
+    // This and following subsets on this path will always add up to
+    // greater than targetSum, so no need to continue
+    if (sum > targetSum) return [];
+
+    // Initialize results array. Will contain only valid subsets
+    let results = [];
+
+    // Slice gets from the set all the elements at the right of the last element
+    // to be evaluated (last element of subset)
+    // forEach iterated on the resulting array
+    set.slice(setindex).forEach((num, index) => {
+      // The next subset to be evaluated, current subset plus next element
+      const nextSubset = [...subset, num];
+
+      // Next index from the set. Current set index plus iteration index
+      // index starts at 0, so a + 1 is required 
+      const nextSetIndex = setindex + index + 1;
+
+      // Sum of elements from the next subset to be evaluated
+      const nextSum = sum + num;
+
+      // Call recursively the subsetSum for the nextSubset
+      const subsetResult = subsetSum(
+        set,
+        nextSubset,
+        nextSetIndex,
+        nextSum,
+        targetSum
+      );
+
+      // Concat the recursive result with current result arary
+      results = [...results, ...subsetResult];
+    });
+
+    //Return results
+    return results;
+  };
+
+  /*
+   * Example with ordered array
+   *   W = [2, 5, 7, 8, 12, 16, 23, 40]
+   *   K = 25
+   *  
+   *   resulting subsets = [ 2, 7, 16 ], [ 2, 23 ], [ 5, 8, 12 ]
+   */
+
+  const nums = [2, 5, 7, 8, 12, 16, 23, 40];
+
+  const subsets = subsetSum(nums, [], 0, 0, 25);
+
+  console.log(subsets);
+