day 2 solution

2020/Program.cs

@@ -63,8 +63,58 @@ namespace AdventOfCode {
       Assert.Equal(140379120, Day1Part2(testInput));
     }
 
+    static bool IsPasswordValid1(string spec) {
+      string[] tokens = spec.Split(' ');
+      string[] numbers = tokens[0].Split('-');
+      int min = int.Parse(numbers[0]);
+      int max = int.Parse(numbers[1]);
+      char required = tokens[1][0];
+      string password = tokens[2];
+
+      int count = 0;
+      for (int i = 0; i < password.Length; i++) {
+        if (password[i] == required) {
+          count++;
+        }
+      }
+      return min <= count && count <= max;
+    }
+
+    static bool IsPasswordValid2(string spec) {
+      string[] tokens = spec.Split(' ');
+      string[] numbers = tokens[0].Split('-');
+      int lowIndex = int.Parse(numbers[0]) - 1;
+      int highIndex = int.Parse(numbers[1]) - 1;
+      char required = tokens[1][0];
+      string password = tokens[2];
+      return
+        (password[lowIndex] == required && password[highIndex] != required) ||
+        (password[lowIndex] != required && password[highIndex] == required);
+    }
+
+    static int Day2Part1() {
+      return File.ReadAllLines(RootDir + "day02.txt").Count(IsPasswordValid1);
+    }
+
+    static int Day2Part2() {
+      return File.ReadAllLines(RootDir + "day02.txt").Count(IsPasswordValid2);
+    }
+
+    [Fact]
+    static void Day2Test() {
+      Assert.True(IsPasswordValid1("1-3 a: abcde"));
+      Assert.False(IsPasswordValid1("1-3 b: cdefg"));
+      Assert.True(IsPasswordValid1("2-9 c: ccccccccc"));
+      Assert.Equal(603, Day2Part1());
+
+      Assert.True(IsPasswordValid2("1-3 a: abcde"));
+      Assert.False(IsPasswordValid2("1-3 b: cdefg"));
+      Assert.False(IsPasswordValid2("2-9 c: ccccccccc"));
+      Assert.Equal(404, Day2Part2());
+    }
+
     static void Main(string[] args) {
-      Day1Test();
+      Day2Test();
     }
   }
 }