feat[2020-day-01]: find matching expenses in expense report

Finds matching expenses in an array matching a checksum

Author: developher-net

2020/day-01/expenseValidation.js

@@ -0,0 +1,32 @@
+
+/**
+ * Validates a list of records by comparing every combination
+ * to the checksum. Stops when the first match is found
+ */
+const validateRecords = (records, checksum = 2020) => {
+  const results = []
+
+  // We're using Array.find() at each level so it stops looping
+  // onced matched. This game has a habit of throwing huge
+  // data sets to discourage brute-forcing
+  const matcher = records.find((record) => {
+    const match = records.find(matchRec => record + matchRec === checksum)
+    if (match) {
+      results.push(match)
+      return true
+    }
+    return false
+  })
+  if (matcher) {
+    results.push(matcher)
+  }
+
+  if (results.length < 2) {
+    throw new Error('Couldn\'t find a checksum match')
+  }
+  return results
+}
+
+module.exports = {
+  validateRecords
+}