advent of code

solutions/advent-of-code/src/Problem1.java

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+package src;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.util.ArrayList;
+
+public class Problem1 {
+
+    public static void main(String[] args) {
+        ArrayList<String> allLines = new ArrayList<>();
+
+        try (BufferedReader reader = new BufferedReader(new FileReader("inputs/inputProblem1.txt"))) {
+            String line;
+            while ((line = reader.readLine()) != null) {
+                allLines.add(line);
+            }
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+
+        // Call solve and print result
+        System.out.println(solve(allLines));
+    }
+
+    public static int solve(ArrayList<String> allLines) {
+        int dial = 50;
+
+        int total = 0;
+
+        for (String line : allLines) {
+            int value = Integer.parseInt(line.substring(1));
+            if (line.charAt(0)=='L'){
+                System.out.println("Turned Left: " + value);
+                dial -= value;
+            } else {
+                System.out.println("Turned Right: " + value);
+                dial += value;
+            }
+            
+            int num = (dial % 100 + 100) % 100; // Ensure num is between 0-99
+            System.out.println("Current Dial Position: " + num);
+
+            if (num == 0) {
+                total++;
+            }
+
+        }
+
+        return total;
+    }
+}

solutions/advent-of-code/src/Problem1b.java

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+package src;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.util.ArrayList;
+
+public class Problem1b {
+
+    public static void main(String[] args) {
+        ArrayList<String> allLines = new ArrayList<>();
+
+        try (BufferedReader reader = new BufferedReader(new FileReader("inputs/inputProblem1.txt"))) {
+            String line;
+            while ((line = reader.readLine()) != null) {
+                allLines.add(line);
+            }
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+
+        // Call solve and print result
+        System.out.println(solve(allLines));
+    }
+
+    public static int solve(ArrayList<String> allLines) {
+        int dial = 50;  // starting position
+        int total = 0;
+
+        for (String line : allLines) {
+            int value = Integer.parseInt(line.substring(1));
+            int direction = (line.charAt(0) == 'L') ? -1 : 1;
+
+            // Step through each click to count zeros correctly
+            for (int step = 0; step < value; step++) {
+                dial = (dial + direction + 100) % 100; // wrap around 0-99
+                if (dial == 0) {
+                    total++;
+                }
+            }
+
+            System.out.println("Current Dial Position: " + dial + " || Total: " + total);
+        }
+
+        return total;
+    }
+}

solutions/advent-of-code/src/Problem2.java

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+package src;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+public class Problem2 {
+
+    public static void main(String[] args) {
+        String filePath = "inputs/inputProblem2.txt";
+
+        try {
+            String input = readFileAsString(filePath);
+            List<long[]> ranges = parseRanges(input);
+            long tally = solve(ranges);
+            System.out.println("Sum of invalid IDs: " + tally);
+
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    // Solve by generating only repeated IDs
+    public static long solve(List<long[]> ranges) {
+        long sum = 0;
+
+        for (long[] range : ranges) {
+            long start = range[0];
+            long end = range[1];
+
+            for (long num = start; num <= end; num++) {
+                String numStr = String.valueOf(num);
+                int len = numStr.length();
+
+                if (len % 2 != 0) continue;
+
+                boolean repeated = false;
+                for (int prefixLen = 1; prefixLen <= len / 2; prefixLen++) {
+                    if (len % prefixLen != 0) continue; // must divide evenly
+
+                    String prefix = numStr.substring(0, prefixLen);
+                    String repeatedNum = prefix + prefix;
+                    if (repeatedNum.equals(numStr)) {
+                        repeated = true;
+                        break;
+                    }
+                }
+
+                if (repeated) sum += num;
+            }
+        }
+
+        return sum;
+    }
+
+    public static String readFileAsString(String filePath) throws IOException {
+        StringBuilder sb = new StringBuilder();
+        try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
+            String line;
+            while ((line = reader.readLine()) != null) {
+                sb.append(line.trim());
+            }
+        }
+        return sb.toString();
+    }
+
+    public static List<long[]> parseRanges(String input) {
+        List<long[]> result = new ArrayList<>();
+        String[] ranges = input.split(",");
+
+        for (String range : ranges) {
+            String[] parts = range.trim().split("-");
+            if (parts.length != 2) {
+                throw new IllegalArgumentException("Invalid range: " + range);
+            }
+            long start = Long.parseLong(parts[0]);
+            long end = Long.parseLong(parts[1]);
+            result.add(new long[]{start, end});
+        }
+
+        return result;
+    }
+}

solutions/advent-of-code/src/Problem2b.java

@@ -0,0 +1,87 @@
+package src;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+public class Problem2b {
+
+    public static void main(String[] args) {
+        String filePath = "inputs/inputProblem2.txt";
+
+        try {
+            String input = readFileAsString(filePath);
+            List<long[]> ranges = parseRanges(input);
+            long tally = solve(ranges);
+            System.out.println("Sum of invalid IDs: " + tally);
+
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+    public static long solve(List<long[]> ranges) {
+        long sum = 0;
+
+        for (long[] range : ranges) {
+            long start = range[0];
+            long end = range[1];
+
+            for (long num = start; num <= end; num++) {
+                String numStr = String.valueOf(num);
+                int len = numStr.length();
+
+                boolean repeated = false;
+
+                for (int prefixLen = 1; prefixLen <= len / 2; prefixLen++) {
+                    if (len % prefixLen != 0) continue;
+
+                    String prefix = numStr.substring(0, prefixLen);
+                    int times = len / prefixLen;
+                    StringBuilder sb = new StringBuilder();
+                    for (int t = 0; t < times; t++) {
+                        sb.append(prefix);
+                    }
+
+                    if (sb.toString().equals(numStr)) {
+                        repeated = true;
+                        break;
+                    }
+                }
+
+                if (repeated) sum += num;
+            }
+        }
+
+        return sum;
+    }
+
+    public static String readFileAsString(String filePath) throws IOException {
+        StringBuilder sb = new StringBuilder();
+        try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
+            String line;
+            while ((line = reader.readLine()) != null) {
+                sb.append(line.trim());
+            }
+        }
+        return sb.toString();
+    }
+
+    public static List<long[]> parseRanges(String input) {
+        List<long[]> result = new ArrayList<>();
+        String[] ranges = input.split(",");
+
+        for (String range : ranges) {
+            String[] parts = range.trim().split("-");
+            if (parts.length != 2) {
+                throw new IllegalArgumentException("Invalid range: " + range);
+            }
+            long start = Long.parseLong(parts[0]);
+            long end = Long.parseLong(parts[1]);
+            result.add(new long[]{start, end});
+        }
+
+        return result;
+    }
+}

solutions/advent-of-code/src/Problem3.java

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+package src;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+
+public class Problem3 {
+
+    public static void main(String[] args) {
+        String filePath = "inputs/inputProblem3.txt";
+        try (BufferedReader reader = new BueredReader(new FileReader(filePath))) {
+            String line;
+            long total = 0;
+            while ((line = reader.readLine()) != null) {
+                total += maxTwoDigit(line);
+            }
+            System.out.println(total);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public static int maxTwoDigit(String digits) {
+        int maxDigit = -1;
+        int maxValue = 0;
+        for (char c : digits.toCharArray()) {
+            int digit = c - '0';
+            if (maxDigit >= 0) {
+                int value = maxDigit * 10 + digit;
+                if (value > maxValue) {
+                    maxValue = value;
+                }
+            }
+            if (digit > maxDigit) {
+                maxDigit = digit;
+            }
+        }
+
+        return maxValue;
+    }
+}

solutions/advent-of-code/src/Problem3b.java

@@ -0,0 +1,39 @@
+package src;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+
+public class Problem3b {
+
+    public static void main(String[] args) {
+        String filePath = "inputs/inputProblem3.txt";
+        try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
+            String line;
+            long total = 0;
+            while ((line = reader.readLine()) != null) {
+                String maxDigits = maxKDigitsString(line, 12);
+                total += Long.parseLong(maxDigits);
+            }
+            System.out.println(total);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public static String maxKDigitsString(String digits, int k) {
+        int n = digits.length();
+        char[] stack = new char[k];
+        int top = 0;
+        for (int i = 0; i < n; i++) {
+            char c = digits.charAt(i);
+            while (top > 0 && stack[top - 1] < c && (top - 1 + (n - i)) >= k) {
+                top--;
+            }
+            if (top < k) {
+                stack[top++] = c;
+            }
+        }
+        return new String(stack, 0, k);
+    }
+}