fix[2020-day-01]: find the exact number of desired expense records

If the desired number is 3, don't stop if 2 meet the checksum requirements.

Author: developher-net

2020/day-01/expenseValidation.js

@@ -23,8 +23,8 @@ const validateRecords = (records, checksum = 2020, goal = 2) => {
     this.depth = this.depth || 1 // depth tracking starts at level 1
     this.tracker = this.tracker || 0 // for basic sums, start counter at 0
     const subTotal = this.tracker + record
-    // Found a match, don't keep searching!
-    if (subTotal === this.target) {
+    // Found a match in the specified with desired qty of results, don't keep searching!
+    if (subTotal === this.target && this.depth >= goal) {
       results.push(record)
       return true
     }
@@ -44,7 +44,7 @@ const validateRecords = (records, checksum = 2020, goal = 2) => {
       depth: this.depth + 1,
       tracker: this.tracker + record
     })
-    // Children matched, so record this one as well
+    // Propogate maches back up the recursion chain, capturing each
     if (res) {
       results.push(record)
       return true

2020/day-01/expenseValidation.test.js

@@ -23,6 +23,16 @@ describe('--- 2020 Day 1: Report Repair ---', () => {
           expect(testData.indexOf(result)).to.be.greaterThan(-1)
         })
       })
+      it('it can find a specified number of records adding up to 2020', () => {
+        const expected = [979, 366, 675]
+        const results = validateRecords(testData, undefined, 3)
+        // Should same number of results
+        expect(results.length).to.equal(expected.length)
+        // Result order is unnecessary, but all expected hould be in the result set
+        expected.forEach(result => {
+          expect(testData.indexOf(result)).to.be.greaterThan(-1)
+        })
+      })
       it('it supports specifying an alternate checksum', () => {
         const arrSum = (arr) => arr.reduce((x, y) => x + y, 0)
         const expected = [testData[3], testData[5]]