Day 3: Binary Diagnostic ratings + math utils

Author: Inusette

Advent_2021/src/main/java/Day03/BinaryPowerConsumptionDiagnoser.java

@@ -0,0 +1,61 @@
+package Day03;
+
+import advent.utils.AdventMathUtils;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class BinaryPowerConsumptionDiagnoser {
+
+    public long diagnoseBinaryPowerConsumption(List<String> binaryReportEntries) {
+        int reportSize = binaryReportEntries.get(0).length();
+        StringBuilder gamma = new StringBuilder();
+        StringBuilder epsilon = new StringBuilder();
+        for (int bitPosition = 0; bitPosition < reportSize; bitPosition++) {
+            char mostFrequentAtPos = getMostFrequentElementAtPosition(binaryReportEntries, bitPosition);
+            gamma.append(mostFrequentAtPos);
+            epsilon.append(mostFrequentAtPos == '1' ? '0' : '1');
+        }
+        return multiplyRates(gamma.toString(), epsilon.toString());
+    }
+
+    public long diagnoseLifeSupportRating(List<String> reportEntries) {
+        List<String> oxygenRate = new ArrayList<>(List.copyOf(reportEntries));
+        List<String> cO2Rate = new ArrayList<>(List.copyOf(reportEntries));
+        int reportSize = reportEntries.get(0).length();
+
+        for (int bitPosition = 0; bitPosition < reportSize; bitPosition++) {
+            char mostFrequentOxygenElement = getMostFrequentElementAtPosition(oxygenRate, bitPosition);
+            char leastFrequentCo2Element = getMostFrequentElementAtPosition(cO2Rate, bitPosition) == '1' ? '0' : '1';
+
+            int finalBitPosition = bitPosition;
+            if (oxygenRate.size() > 1) {
+                oxygenRate.removeIf(p -> p.charAt(finalBitPosition) != mostFrequentOxygenElement);
+            }
+            if (cO2Rate.size() > 1) {
+                cO2Rate.removeIf(p -> p.charAt(finalBitPosition) != leastFrequentCo2Element);
+            }
+            if (cO2Rate.size() == 1 && oxygenRate.size() == 1) {
+                break;
+            }
+        }
+        return multiplyRates(oxygenRate.get(0), cO2Rate.get(0));
+    }
+
+    private long multiplyRates(String s, String s2) {
+        return Integer.parseInt(s, 2) * Integer.parseInt(s2, 2);
+    }
+
+    private char getMostFrequentElementAtPosition(List<String> reportEntries, int bitPosition) {
+        List<Character> currentPositionList = new ArrayList<>();
+        for (String currentReport : reportEntries) {
+            currentPositionList.add(currentReport.charAt(bitPosition));
+        }
+        List<Character> mostFrequentElementsInList = AdventMathUtils.findMostFrequentElementsInList(currentPositionList);
+        if (mostFrequentElementsInList.size() == 1) {
+            return mostFrequentElementsInList.get(0);
+        } else {
+            return '1';
+        }
+    }
+}

Advent_2021/src/main/java/Day03/Day03Main.java

@@ -0,0 +1,24 @@
+package Day03;
+
+import advent.utils.AdventFileUtils;
+
+import java.util.List;
+
+public class Day03Main {
+
+    public static void main(String[] args) {
+        List<String> inputAsStringList = getInput();
+        System.out.println("This is the input: \n" + inputAsStringList);
+        BinaryPowerConsumptionDiagnoser diagnoser = new BinaryPowerConsumptionDiagnoser();
+
+        long powerConsumptionRating = diagnoser.diagnoseBinaryPowerConsumption(inputAsStringList);
+        System.out.println("The power consumption rating is: " + powerConsumptionRating);
+
+        long lifeSupportRating = diagnoser.diagnoseLifeSupportRating(inputAsStringList);
+        System.out.println("The life support rating is: " + lifeSupportRating);
+    }
+
+    protected static List<String> getInput() {
+        return AdventFileUtils.readClassInputIntoStringLines(Day03Main.class);
+    }
+}

Advent_2021/src/main/java/advent/utils/AdventMathUtils.java

@@ -1,7 +1,14 @@
 package advent.utils;
 
+import java.util.Collections;
+import java.util.Comparator;
 import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
 import java.util.Set;
+import java.util.function.BinaryOperator;
+import java.util.function.Function;
+import java.util.stream.Collectors;
 
 public class AdventMathUtils {
 
@@ -15,6 +22,19 @@ public static <T> Set<T> getIntersectionOf(Set<T> firstSet, Set<T> secondSet) {
         return intersection;
     }
 
+    public static <T> T calculateMode(List<T> elements) {
+        return elements.stream()
+                .reduce(BinaryOperator.maxBy(Comparator.comparingInt(o -> Collections.frequency(elements, o)))).orElse(null);
+    }
+
+    public static <T> List<T> findMostFrequentElementsInList(List<T> elements) {
+        return elements.stream().collect(Collectors.groupingBy(Function.identity(), Collectors.counting()))
+                .entrySet().stream()
+                .collect(Collectors.groupingBy(Map.Entry::getValue, Collectors.mapping(Map.Entry::getKey, Collectors.toList())))
+                .entrySet().stream().max(Map.Entry.comparingByKey()).map(Map.Entry::getValue)
+                .orElse(Collections.emptyList());
+    }
+
     public static boolean isSumOfElements(long sum, long element1, long element2) {
         return element1 + element2 == sum;
     }