Create Day2.java

Author: nsiwnf

Day2.java

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+
+/**
+ * --- Day 2: Corruption Checksum ---
+ * 
+ * As you walk through the door, a glowing humanoid shape yells in your
+ * direction. "You there! Your state appears to be idle. Come help us repair the
+ * corruption in this spreadsheet - if we take another millisecond, we'll have
+ * to display an hourglass cursor!"
+ * 
+ * The spreadsheet consists of rows of apparently-random numbers. To make sure
+ * the recovery process is on the right track, they need you to calculate the
+ * spreadsheet's checksum. For each row, determine the difference between the
+ * largest value and the smallest value; the checksum is the sum of all of these
+ * differences.
+ * 
+ * For example, given the following spreadsheet:
+ *
+ * 5 1 9 5
+ * 7 5 3
+ * 2 4 6 8
+ * 
+ * The first row's largest and smallest values are 9 and 1, and their difference is 8.
+ * The second row's largest and smallest values are 7 and 3, and their difference is 4.
+ * The third row's difference is 6.
+ * In this example, the spreadsheet's checksum would be 8 + 4 + 6 = 18.
+ */
+public class Day2 {
+
+  public static int part1(String input) {
+    String[] rows = input.split("\n");
+    int result = 0;
+    for (String row : rows) {
+      int max = -1;
+      int min = Integer.MAX_VALUE;
+      String[] numbers = row.split("\t");
+      for (String number : numbers) {
+        int n = Integer.parseInt(number);
+        if (max < n) {
+          max = n;
+        }
+        if (min > n) {
+          min = n;
+        }
+      }
+      result += (max - min);
+    }
+
+    return result;
+  }
+
+  /**
+   * Evenly divisible
+   * 
+   * @param input
+   * @return
+   */
+  public static int part2(String input) {
+    String[] rows = input.split("\n");
+    int result = 0;
+    for (String row : rows) {
+      String[] numbers = row.split("\t");
+      result += addDivisibles(0, 1, numbers);
+    }
+
+    return result;
+  }
+  
+  private static int addDivisibles(int i, int j, String[] numbers) {
+    if (i < j && j < numbers.length) {
+      int a = Integer.parseInt(numbers[i]);
+      int b = Integer.parseInt(numbers[j]);
+
+      int d = addDivisible(a, b);
+      if (d == 0) {
+        int x = addDivisibles(i + 1, j, numbers);
+        if (x == 0)
+          return addDivisibles(i, j + 1, numbers);
+        else
+          return x;
+      }
+      else
+        return d;
+    }
+    else
+      return 0;
+  }
+
+  private static int addDivisible(int n, int m) {
+    if (n % m == 0) {
+      return n / m;
+    }
+    else if (m % n == 0) {
+      return m / n;
+    }
+    return 0;
+  }