2024 Day 2 part 1 start

Author: leibi

Diff for: src/main/java/net/leibi/adventofcode2024/day1/Day1.java

@@ -30,7 +30,7 @@ public Integer getSumOfDistances(List<Integer> left, List<Integer> right) {
         left.sort(Integer::compareTo);
         right.sort(Integer::compareTo);
 
-        Integer sum = 0;
+        int sum = 0;
         for (var i = 0; i < left.size(); i++) {
             sum += Math.abs(left.get(i) - right.get(i));
         }
@@ -41,19 +41,28 @@ public Integer getSumOfDistances(List<Integer> left, List<Integer> right) {
     public long part2(String input) {
 
         var lists = getListOfListsFromInput(input);
-        var scores = getSimilarityScores(lists.get(0), lists.get(1));
+        int[] rightArray = lists.get(1).stream().mapToInt(Integer::intValue).toArray();
+        var scores = getSimilarityScores(lists.get(0), rightArray);
 
         return scores.stream().mapToLong(i -> i).sum();
     }
 
-    private List<Long> getSimilarityScores(List<Integer> left, List<Integer> right) {
+    private List<Long> getSimilarityScores(List<Integer> left, int[] right) {
 
         var scores = new ArrayList<Long>();
-        for (var i : left) {
-            final var count = right.stream().filter(v -> v.equals(i)).count();
-            var score = count * i;
-            scores.add(score);
+
+
+        for (var currentNumber : left) {
+            scores.add(getCountOfOccurancesOfNumberInList(right, currentNumber) * currentNumber);
         }
         return scores;
     }
+
+    private static long getCountOfOccurancesOfNumberInList(int[] right, int i) {
+        long cnt = 0;
+        for (int integer : right) {
+            if (i == integer) cnt++;
+        }
+        return cnt;
+    }
 }

Diff for: src/main/java/net/leibi/adventofcode2024/day2/Day2.java

@@ -0,0 +1,36 @@
+package net.leibi.adventofcode2024.day2;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class Day2 {
+    public long part1(String input) {
+        final var list = input.lines().map(s -> s.split("\\s+")).toList();
+        return list.stream().filter(a -> isSafe(Arrays.asList(a))).count();
+    }
+
+    boolean isSafe(List<Integer> report) {
+
+        int minSafe = 1;
+        int maxSafe = 3;
+
+        Direction direction = report.get(1) - report.get(0) > 0 ? Direction.INC : Direction.DEC;
+        for (var i = 1; i < report.size(); i++) {
+            var diff = report.get(i) - report.get(i - 1);
+            if (Math.abs(diff) > maxSafe || Math.abs(diff) < minSafe)
+                return false;
+
+            Direction localDir = diff > 0 ? Direction.INC : Direction.DEC;
+            if (localDir != direction)
+                return false;
+        }
+        return true;
+    }
+
+    enum Direction {
+        INC,
+        DEC,
+        BOTH
+    }
+
+}

Diff for: src/main/java/net/leibi/adventofcode2024/day2/Input.java

@@ -0,0 +1,13 @@
+package net.leibi.adventofcode2024.day2;
+
+public class Input {
+
+    public static final String SMALL = """
+            7 6 4 2 1
+            1 2 7 8 9
+            9 7 6 2 1
+            1 3 2 4 5
+            8 6 4 4 1
+            1 3 6 7 9
+            """;
+}

Diff for: src/test/java/net/leibi/adventofcode2024/day2/Day2Test.java

@@ -0,0 +1,33 @@
+package net.leibi.adventofcode2024.day2;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class Day2Test {
+
+
+    private final Day2 day2 = new Day2();
+
+    @Test
+    void part1Small(){
+        assertThat((day2.part1(Input.SMALL))).isEqualTo(2L);
+    }
+
+
+    @Test
+    void isSafe(){
+
+        assertThat(day2.isSafe(List.of(7,6,4,2,1))).isTrue();
+        assertThat(day2.isSafe(List.of(1,2,7,8,9))).isFalse();
+        assertThat(day2.isSafe(List.of(9,7,6,2,1))).isFalse();
+        assertThat(day2.isSafe(List.of(1,3,2,4,5))).isFalse();
+        assertThat(day2.isSafe(List.of(8,6,4,4,1))).isFalse();
+        assertThat(day2.isSafe(List.of(1,3,6,7,9))).isTrue();
+
+
+    }
+
+}