1 files changed, 46 insertions, 0 deletions
diff --git a/day21/day21-2.js b/day21/day21-2.js
new file mode 100644
index 0000000..a5c697f
--- /dev/null
+++ b/day21/day21-2.js
@@ -0,0 +1,46 @@
+const data = require('./data')
+let arr = data
+  .split(/\n/g).filter(Boolean)
+  .map(l => l.replace(')','').split(' (contains '))
+  .map(l => [l[0].split(' '), l[1].split(', ')])
+
+const ingredients = {}
+const allergens = {}
+
+for (let i=0; i<arr.length; i++) {
+  for (let j=0; j<arr[i][0].length; j++) {
+    let ingredient = arr[i][0][j]
+    if (!ingredients[ingredient]) { ingredients[ingredient] = [] }
+    ingredients[ingredient].push(i)
+  }
+  for (let k=0; k<arr[i][1].length; k++) {
+    let allergen = arr[i][1][k]
+    if (!allergens[allergen]) { allergens[allergen] = [] }
+    allergens[allergen].push(i)
+  }
+}
+
+const variants = {}
+  Object.values(allergens).forEach((allergen, i) => {
+  const iv = Object.entries(ingredients).filter(i => allergen.every(a => i[1].includes(a)))
+  if (iv) { variants[Object.keys(allergens)[i]] = iv }
+})
+
+while (Object.values(variants).some(iv => iv.length > 1)) {
+  Object.entries(variants).forEach(iv => {
+    if (iv[1].length === 1) {
+      Object.keys(variants).forEach(ik => {
+        if (ik !== iv[0]) {
+          variants[ik] = variants[ik].filter(x => x[0] != iv[1][0][0])
+        }
+      })
+    }
+  })
+}
+
+const result = Object.entries(variants)
+  .sort((a, b) => a[0].localeCompare(b[0]))
+  .map(r => r[1][0][0])
+  .join(',')
+
+console.log('Answer: ', result)