work with 2 numbers

Author: amejiarosario

src/algorithms/combination-sum.js

@@ -17,15 +17,22 @@ function combinationSum(
 
   let candidate = candidates[index];
   let newSum = currentSum + candidate;
+  let newCurrent = current.concat(candidate);
 
   if (newSum <= target) {
-    combinationSum(candidates, target, solution, current.concat(candidate), newSum, index);
+    combinationSum(candidates, target, solution, newCurrent, newSum, index);
   } else if (index < candidates.length - 1) {
     const newIndex = index + 1;
-    while (currentSum + candidates[newIndex] > target) current.pop();
     candidate = candidates[newIndex];
-    newSum = currentSum + candidate;
-    combinationSum(candidates, target, solution, current.concat(candidate), newSum, newIndex);
+    newSum = currentSum;
+    const reducedCurrent = current.slice(); // clone current
+    while (newSum + candidate > target) {
+      const deletedCandidate = reducedCurrent.pop();
+      newSum -= deletedCandidate;
+    }
+    newSum += candidate;
+    newCurrent = reducedCurrent.concat(candidate);
+    combinationSum(candidates, target, solution, newCurrent, newSum, newIndex);
   }
 
 

src/algorithms/combination-sum.spec.js

@@ -4,4 +4,23 @@ describe('combinationSum', () => {
   it('should return empty', () => {
     expect(combinationSum([], 0)).toEqual([[]]);
   });
+
+  it('should find solution for one item', () => {
+    expect(combinationSum([1], 1)).toEqual([[1]]);
+  });
+
+  it('should use multiple times one value', () => {
+    expect(combinationSum([1], 2)).toEqual([[1, 1]]);
+  });
+
+  it('should not find solution', () => {
+    expect(combinationSum([2], 1)).toEqual([]);
+  });
+
+  fit('should not find solution', () => {
+    expect(combinationSum([1, 2], 3)).toEqual([
+      [1, 1, 1],
+      [1, 2],
+    ]);
+  });
 });