Solve day 2

src/day02.zig

@@ -0,0 +1,101 @@
+const std = @import("std");
+
+pub const input = @embedFile("input/day02.txt");
+const test_input = @embedFile("input/day02_test1.txt");
+
+var gpa = std.heap.GeneralPurposeAllocator(.{ .safety = true }){};
+const allocator = gpa.allocator();
+
+const Choice = enum(usize) {
+    Rock = 1,
+    Paper = 2,
+    Scissors = 3,
+    fn from_opponent_char(char: u8) Choice {
+        return switch (char) {
+            'A' => Choice.Rock,
+            'B' => Choice.Paper,
+            'C' => Choice.Scissors,
+            else => @panic("invalid opponent char!"),
+        };
+    }
+    fn from_me_char(char: u8) Choice {
+        return switch (char) {
+            'X' => Choice.Rock,
+            'Y' => Choice.Paper,
+            'Z' => Choice.Scissors,
+            else => @panic("invalid me char!"),
+        };
+    }
+    fn from_outcome(self: Choice, outcome_char: u8) Choice {
+        return switch (outcome_char) {
+            'X' => self.lose_choice(),
+            'Y' => self,
+            'Z' => self.win_choice(),
+            else => @panic("invalid outcome char!"),
+        };
+    }
+    fn lose_choice(self: Choice) Choice {
+        return switch (self) {
+            Choice.Rock => Choice.Scissors,
+            Choice.Paper => Choice.Rock,
+            Choice.Scissors => Choice.Paper,
+        };
+    }
+    fn win_choice(self: Choice) Choice {
+        return switch (self) {
+            Choice.Rock => Choice.Paper,
+            Choice.Paper => Choice.Scissors,
+            Choice.Scissors => Choice.Rock,
+        };
+    }
+    fn beats(self: Choice, other: Choice) bool {
+        return if (other.win_choice() == self) true else false;
+    }
+    fn ties(self: Choice, other: Choice) bool {
+        return self == other;
+    }
+};
+
+pub fn solve_part1(data: []const u8) usize {
+    var lines = std.mem.split(u8, data, "\n");
+    var score: usize = 0;
+    while (lines.next()) |line| {
+        if (std.mem.eql(u8, line, "")) break;
+        var player_choices = std.mem.split(u8, line, " ");
+        var opponent = Choice.from_opponent_char(player_choices.next().?[0]);
+        var me = Choice.from_me_char(player_choices.next().?[0]);
+        score += @enumToInt(me);
+        if (me.beats(opponent)) {
+            score += 6;
+        } else if (me.ties(opponent)) {
+            score += 3;
+        }
+    }
+    return score;
+}
+
+pub fn solve_part2(data: []const u8) usize {
+    var lines = std.mem.split(u8, data, "\n");
+    var score: usize = 0;
+    while (lines.next()) |line| {
+        if (std.mem.eql(u8, line, "")) break;
+        var player_choices = std.mem.split(u8, line, " ");
+        var opponent = Choice.from_opponent_char(player_choices.next().?[0]);
+        var me = opponent.from_outcome(player_choices.next().?[0]);
+        score += @enumToInt(me);
+        if (me.beats(opponent)) {
+            score += 6;
+        } else if (me.ties(opponent)) {
+            score += 3;
+        }
+    }
+    return score;
+}
+
+test "solves part1" {
+    try std.testing.expectEqual(solve_part1(test_input), 15);
+}
+
+test "solves part2" {
+    try std.testing.expectEqual(solve_part2(test_input), 12);
+}

src/input/day02_test1.txt

@@ -0,0 +1,3 @@
+A Y
+B X
+C Z

src/main.zig

@@ -1,6 +1,7 @@
 const std = @import("std");
 
 const day01 = @import("day01.zig");
+const day02 = @import("day02.zig");
 const utils = @import("utils.zig");
 
 pub fn main() !void {
@@ -25,6 +26,22 @@ pub fn main() !void {
         try stdout.print("Part 2: {} ({d:.2} {s})\n", .{ part2, part2_time.value, part2_time.unit.abbr() });
     }
 
+    {
+        try stdout.print("\nDay 2\n", .{});
+
+        const part1_start = timer.read();
+        var part1 = day02.solve_part1(day02.input);
+        const part1_end = timer.read();
+        const part1_time = utils.HumanTime.new(part1_end - part1_start);
+        try stdout.print("Part 1: {} ({d:.2} {s})\n", .{ part1, part1_time.value, part1_time.unit.abbr() });
+
+        const part2_start = timer.read();
+        var part2 = day02.solve_part2(day02.input);
+        const part2_end = timer.read();
+        const part2_time = utils.HumanTime.new(part2_end - part2_start);
+        try stdout.print("Part 2: {} ({d:.2} {s})\n", .{ part2, part2_time.value, part2_time.unit.abbr() });
+    }
+
     try bw.flush();
 }
 
@@ -32,5 +49,6 @@ test {
     std.testing.refAllDecls(@This());
 
     _ = day01;
+    _ = day02;
     _ = utils;
 }