Add ES6 Examples to all chapters (#38)

* add ES6 example for binary search

* add ES6 example for selection sort

* add ES6 example for countdown

* add ES6 example for greet

* add ES6 example for factorial

* edit ES6 example for quicksort

* add ES6 example for loop sum

* add ES6 example for recursive sum

* add ES6 example for recursive count

* add ES6 example for recursive max

* add ES6 example for price of groceries

* add ES6 example for check voter

* add ES6 example for breadth-first search

* add ES6 example for dijkstras algorithm

* edit ES6 example for dijkstras algorithm

* edit ES6 example for set covering

* add ES6 example for longest common subsequence

08_greedy_algorithms/ES6/01_set_covering.js

@@ -0,0 +1,29 @@
+// You pass an array in, and it gets converted to a set.
+let statesNeeded = new Set(['mt', 'wa', 'or', 'id', 'nv', 'ut', 'ca', 'az']);
+
+const stations = {};
+stations.kone = new Set(['id', 'nv', 'ut']);
+stations.ktwo = new Set(['wa', 'id', 'mt']);
+stations.kthree = new Set(['or', 'nv', 'ca']);
+stations.kfour = new Set(['nv', 'ut']);
+stations.kfive = new Set(['ca', 'az']);
+
+const finalStations = new Set();
+
+
+while (statesNeeded.size) {
+  let bestStation = null;
+  let statesCovered = new Set();
+  Object.keys(stations).forEach((station) => {
+    const states = stations[station];
+    const covered = new Set([...statesNeeded].filter(x => states.has(x)));
+    if (covered.size > statesCovered.size) {
+      bestStation = station;
+      statesCovered = covered;
+    }
+  });
+  statesNeeded = new Set([...statesNeeded].filter(x => !statesCovered.has(x)));
+  finalStations.add(bestStation);
+}
+
+console.log(finalStations); // Set { 'kone', 'ktwo', 'kthree', 'kfive' }