Designed an exhaustive search for the third example problem.

exhaustive-search.md

@@ -113,22 +113,24 @@ set of items not exceeding the weight limit.
 
 Signature: knapsack(I: set<item>, w: set<item> → number, W: number, v: set<item> → number) → K: set<item>
 Happy path:
- Precondition:
- Postcondition:
- Postcondition:
+ Precondition: |options(I, w, W)| > 0
+ Postcondition: K ∈ options(I, w, W)
+ Postcondition: ∀X∈options(I, w, W). v(K) ≥ v(X)
 Sad path:
- Precondition:
- Postcondition:
+ Precondition: |options(I, w, W)| = 0
+ Postcondition: K = ⊥
 
 ### JavaScript
 
 ```
 function knapsack(items, getWeight, weightLimit, getValue) {
-  // …
+  let result = undefined;
   for (const option of options(items, getWeight, weightLimit)) {
-    // …
+    if (result === undefined || getValue(option) >= getValue(result)) {
+      result = option;
+    }
   }
-  // …
+  return result;
 }
 ```
 
@@ -144,13 +146,19 @@ of items not exceeding the weight limit.
 
 Signature: options(I: set<item>, w: set<item> → number, W: number) → O: set<set<item>>
 Precondition: [none]
-Postcondition:
-Postcondition:
+Postcondition: O ⊆ 𝒫(I)
+Postcondition: ∀X∈𝒫(I). X∈O ↔ w(X) ≤ W
 
 #### JavaScript
 
 ```
 function options(items, getWeight, weightLimit) {
-  // …
+  const results = new Set();
+  for (const candidate of powerset(items)) {
+    if (getWeight(candidate) <= weightLimit) {
+      results.add(candidate);
+    }
+  }
+  return results;
 }
 ```