Add backtracking solution for finding the power-set of a set.

src/algorithms/sets/power-set/bwPowerSet.js

@@ -0,0 +1,34 @@
+/**
+ * Find power-set of a set using BITWISE approach.
+ *
+ * @param {*[]} originalSet
+ * @return {*[][]}
+ */
+export default function powerSet(originalSet) {
+  const subSets = [];
+
+  // We will have 2^n possible combinations (where n is a length of original set).
+  // It is because for every element of original set we will decide whether to include
+  // it or not (2 options for each set element).
+  const numberOfCombinations = 2 ** originalSet.length;
+
+  // Each number in binary representation in a range from 0 to 2^n does exactly what we need:
+  // it shows by its bits (0 or 1) whether to include related element from the set or not.
+  // For example, for the set {1, 2, 3} the binary number of 0b010 would mean that we need to
+  // include only "2" to the current set.
+  for (let combinationIndex = 0; combinationIndex < numberOfCombinations; combinationIndex += 1) {
+    const subSet = [];
+
+    for (let setElementIndex = 0; setElementIndex < originalSet.length; setElementIndex += 1) {
+      // Decide whether we need to include current element into the subset or not.
+      if (combinationIndex & (1 << setElementIndex)) {
+        subSet.push(originalSet[setElementIndex]);
+      }
+    }
+
+    // Add current subset to the list of all subsets.
+    subSets.push(subSet);
+  }
+
+  return subSets;
+}