Added second day in zig

2021/02/example

@@ -0,0 +1,6 @@
+forward 5
+down 5
+forward 8
+up 3
+down 8
+forward 2

2021/02/first.zig

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+const std = @import("std");
+
+const example = @embedFile("example");
+const input = @embedFile("input");
+
+pub fn main() anyerror!void {
+    const result = try solve(input);
+    try std.io.getStdOut().writer().print("{}\n", .{result});
+}
+
+fn solve(puzzle: []const u8) !u64 {
+    var it = std.mem.tokenize(u8, puzzle, "\n");
+    var pos: u64 = 0;
+    var depth: u64 = 0;
+    while (it.next()) |line| {
+        var it2 = std.mem.tokenize(u8, line, " ");
+        const step = it2.next() orelse unreachable;
+        const n: u64 = std.fmt.parseInt(u64, it2.next().?, 10) catch unreachable;
+        switch (step[0]) {
+            'f' => pos += n,
+            'd' => depth += n,
+            'u' => depth -= n,
+            else => unreachable,
+        }
+    }
+    return pos * depth;
+}
+
+test "solve" {
+    try std.testing.expectEqual(solve(example), 150);
+}

2021/02/second.zig

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+const std = @import("std");
+
+const example = @embedFile("example");
+const input = @embedFile("input");
+
+pub fn main() anyerror!void {
+    const result = try solve(input);
+    try std.io.getStdOut().writer().print("{}\n", .{result});
+}
+
+fn solve(puzzle: []const u8) !u64 {
+    var it = std.mem.tokenize(u8, puzzle, "\n");
+    var aim: u64 = 0;
+    var pos: u64 = 0;
+    var depth: u64 = 0;
+    while (it.next()) |line| {
+        var it2 = std.mem.tokenize(u8, line, " ");
+        const step = it2.next() orelse unreachable;
+        const n: u64 = std.fmt.parseInt(u64, it2.next().?, 10) catch unreachable;
+        switch (step[0]) {
+            'f' => {
+                pos += n;
+                depth += n * aim;
+            },
+            'd' => aim += n,
+            'u' => aim -= n,
+            else => unreachable,
+        }
+    }
+    return pos * depth;
+}
+
+test "solve" {
+    try std.testing.expectEqual(solve(example), 900);
+}