From 8abbc792f613611a7cdb642c42349d83dc89f4ba Mon Sep 17 00:00:00 2001
From: siiky <github-siiky@net-c.cat>
Date: Fri, 31 Jan 2025 13:19:05 +0000
Subject: [PATCH 1/4] fix: target without divisor denoms is no shortcut
 condition

---
 lib/coin-change.js | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/lib/coin-change.js b/lib/coin-change.js
index 1c9eab5e..4a1c964a 100644
--- a/lib/coin-change.js
+++ b/lib/coin-change.js
@@ -24,11 +24,6 @@ const prepare_denominations = denominations =>
 const max_denomination_multiplicity = (denom, count, target) =>
   Math.min(count, Math.floor(target / denom))
 
-const has_divisor = (didx, denominations, target) =>
-  denominations
-    .slice(didx)
-    .some(({ denom }) => (target % denom) === 0)
-
 /*
  * @returns null if there's no solution set;
  *          false if there's no solution;
@@ -78,7 +73,7 @@ const solve = (model, target) => {
        * of the denominations, or if the target is not divisible by any of the
        * denominations
        */
-      if (target > csum || !has_divisor(didx, denominations, target))
+      if (target > csum)
         return memo_set(memo, target, denom, false)
 
       let solution = memo_get(memo, target, denom)

From 91c4ca4dceb65a7b92dab21762a1745d677afa0b Mon Sep 17 00:00:00 2001
From: siiky <github-siiky@net-c.cat>
Date: Mon, 3 Feb 2025 14:34:19 +0000
Subject: [PATCH 2/4] fix: ensure `coin-change` is valid before comparing with
 `subset-sum`

---
 lib/bill-math.js | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/bill-math.js b/lib/bill-math.js
index 8f5daea5..b093fd46 100644
--- a/lib/bill-math.js
+++ b/lib/bill-math.js
@@ -160,13 +160,13 @@ function makeChange(outCassettes, amount) {
   const ss_solution = getSolution_old(outCassettes, amount, BILL_LIST_MODES.VALUE_ROUND_ROBIN)
   const cc_solution = getSolution(outCassettes, amount)
 
-  if (!!ss_solution !== !!cc_solution) {
-    logger.error(new Error(`subset-sum and coin-change don't agree on solvability -- subset-sum:${!!ss_solution} coin-change:${!!cc_solution}`))
+  if (!cc.check(cc_solution, amount.toNumber())) {
+    logger.error(new Error("coin-change provided a bad solution"))
     return solutionToOriginalUnits(ss_solution, outCassettes)
   }
 
-  if (!cc.check(cc_solution, amount.toNumber())) {
-    logger.error(new Error("coin-change provided a bad solution"))
+  if (!!ss_solution !== !!cc_solution) {
+    logger.error(new Error(`subset-sum and coin-change don't agree on solvability -- subset-sum:${!!ss_solution} coin-change:${!!cc_solution}`))
     return solutionToOriginalUnits(ss_solution, outCassettes)
   }
 

From 9ef9a70c39cf097219eb8c8e5ea9b661562b356e Mon Sep 17 00:00:00 2001
From: siiky <github-siiky@net-c.cat>
Date: Mon, 3 Feb 2025 14:36:30 +0000
Subject: [PATCH 3/4] fix: use the same solution format for `subset-sum` as for
 `coin-change`

---
 lib/bill-math.js | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/lib/bill-math.js b/lib/bill-math.js
index b093fd46..8d4515c2 100644
--- a/lib/bill-math.js
+++ b/lib/bill-math.js
@@ -116,14 +116,8 @@ const getSolution_old = (units, amount, mode) => {
   
   const solver = sumService.subsetSum(billList, amount.toNumber())
   const solution = _.countBy(Math.floor, solver.next().value)
-  return _.reduce(
-    (acc, value) => {
-      acc.push({ denomination: _.toNumber(value), provisioned: solution[value] })
-      return acc
-    },
-    [],
-    _.keys(solution)
-  )
+  return Object.entries(solution)
+    .map(([denomination, provisioned]) => [_.toNumber(denomination), provisioned])
 }
 
 const getSolution = (units, amount) => {

From 16e57ee3aba3185e0fe257cf14b54cd0e7137c53 Mon Sep 17 00:00:00 2001
From: siiky <github-siiky@net-c.cat>
Date: Mon, 3 Feb 2025 14:35:16 +0000
Subject: [PATCH 4/4] refactor: simplify reducing solution

---
 lib/bill-math.js | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/lib/bill-math.js b/lib/bill-math.js
index 8d4515c2..f83ff49c 100644
--- a/lib/bill-math.js
+++ b/lib/bill-math.js
@@ -129,24 +129,13 @@ const getSolution = (units, amount) => {
 
 const solutionToOriginalUnits = (solution, units) => {
   const billsToAssign = (count, left) => _.clamp(0, count)(_.isNaN(left) || _.isNil(left) ? 0 : left)
-
-  const billsLeft = _.flow(
-    _.map(([denomination, provisioned]) => [BN(denomination), provisioned]),
-    _.reduce((acc, value) => {
-        acc[value[0]] = (acc[value[0]] || BN(0)).plus(value[1])
-        return acc
-      },
-      {}
-    )
-  )(solution)
-
-  return _.map(
+  const billsLeft = Object.fromEntries(solution)
+  return units.map(
     ({ count, name, denomination }) => {
       const provisioned = billsToAssign(count, billsLeft[denomination])
       billsLeft[denomination] -= provisioned
       return { name, denomination, provisioned }
-    },
-    units
+    }
   )
 }