✨Added Day 3 Part 2 Solution

Day 3/README.md

@@ -48,7 +48,7 @@ Both the oxygen generator rating and the CO2 scrubber rating are values that can
 The **bit criteria** depends on which type of rating value you want to find:
 
 - To find **oxygen generator rating**, determine the **most common** value (`0` or `1`) in the current bit position, and keep only numbers with that bit in that position. If `0` and `1` are equally common, keep values with a `1` in the position being considered.
-- To find **CO2 scrubber rating**, determine the least common value (`0` or `1`) in the current bit position, and keep only numbers with that bit in that position. If `0` and `1` are equally common, keep values with a `0` in the position being considered.
+- To find **CO2 scrubber rating**, determine the **least common** value (`0` or `1`) in the current bit position, and keep only numbers with that bit in that position. If `0` and `1` are equally common, keep values with a `0` in the position being considered.
 
 For example, to determine the **oxygen generator rating** value using the same example diagnostic report from above:
 

Day 3/main.go

@@ -12,9 +12,38 @@ func powInt(x, y int) int {
 	return int(math.Pow(float64(x), float64(y)))
 }
 
-func filter(slice []int, test func(int, int) bool, bitPosition int) (results []int) {
+func getCommonBitValues(reports []int, bitPosition int) (int, int) {
+	bitCounts := 0
+	for _, report := range reports { 
+		power := powInt(2, bitPosition)
+		if power & report == power {
+			bitCounts += 1
+		}
+	}
+
+	mcv := 0
+	lcv := 0
+
+	// Most Common Value
+	if bitCounts >= len(reports) / 2 {
+		mcv = 1
+	} else {
+		mcv = 0
+	}
+	
+	// Least Common Value
+	if bitCounts >= len(reports) / 2 {
+		lcv = 0
+	} else {
+		lcv = 1
+	}
+
+	return mcv, lcv
+}
+
+func filter(slice []int, test func(int, int, int) bool, bitPosition int, bitValue int) (results []int) {
 	for _, element := range slice {
-		if test(element, bitPosition) {
+		if test(element, bitPosition, bitValue) {
 			results = append(results, element)
 		}
 	}
@@ -22,23 +51,11 @@ func filter(slice []int, test func(int, int) bool, bitPosition int) (results []i
 }
 
 func partOne(reports []int, numberOfBits int) {
-	bitCounts := []int {}
 	gammaRate := 0
 	epsilonRate := 0
 
 	for i := 0; i < numberOfBits; i++ {
-		for _, report := range reports { 
-			if len(bitCounts) <= i {
-				bitCounts = append(bitCounts, 0)
-			}
-
-			power := powInt(2, i)
-			if power & report == power {
-				bitCounts[i] += 1
-			}
-		}
-
-		if bitCounts[i] > len(reports) / 2 {
+		if mcv, _ := getCommonBitValues(reports, i); mcv == 1 {
 			gammaRate += powInt(2, i)
 		} else {
 			epsilonRate += powInt(2, i)
@@ -49,7 +66,33 @@ func partOne(reports []int, numberOfBits int) {
 }
 
 func partTwo(reports []int, numberOfBits int) {
-	fmt.Printf("Part Two Answer: %d\n", 0)
+	ogrFilteredReports := reports
+	co2srFilteredReports := reports
+
+	filterTest := func (report, bitPosition, bitValue int) bool {
+		power := powInt(2, bitPosition)
+		return (bitValue == 1 && power & report == power) || (bitValue == 0 && power & report != power)
+	}
+
+	for i := numberOfBits - 1; i >= 0; i-- {
+		mcv, _ := getCommonBitValues(ogrFilteredReports, i)
+
+		if len(ogrFilteredReports) > 1 {
+			ogrFilteredReports = filter(ogrFilteredReports, filterTest, i, mcv)
+		}
+
+		_, lcv := getCommonBitValues(co2srFilteredReports, i)
+
+		if len(co2srFilteredReports) > 1 {
+			co2srFilteredReports = filter(co2srFilteredReports, filterTest, i, lcv)
+		}
+
+		if len(ogrFilteredReports) <= 1 && len(co2srFilteredReports) <= 1 {
+			break
+		}
+	}
+
+	fmt.Printf("Part Two Answer: %d\n", ogrFilteredReports[0] * co2srFilteredReports[0])
 }
 
 func main() {