Implement collatz-conjecture in zig

zig/collatz-conjecture/HELP.md

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+# Help
+
+## Running the tests
+
+Write your code in `<exercise_name>.zig`.
+
+To run the tests for an exercise, run:
+
+```bash
+zig test test_exercise_name.zig
+```
+
+in the exercise's root directory (replacing `exercise_name` with the name of the exercise).
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit collatz_conjecture.zig` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Zig track's documentation](https://exercism.org/docs/tracks/zig)
+- The [Zig track's programming category on the forum](https://forum.exercism.org/c/programming/zig)
+- [Exercism's programming category on the forum](https://forum.exercism.org/c/programming/5)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+- [The Zig Programming Language Documentation][documentation] is a great overview of all of the language features that Zig provides to those who use it.
+- [Zig Learn][zig-learn] is an excellent primer that explains the language features that Zig has to offer.
+- [Ziglings][ziglings] is highly recommended.
+  Learn Zig by fixing tiny broken programs.
+- [The Zig Programming Language Discord][discord-zig] is the main [Discord][discord].
+  It provides a great way to get in touch with the Zig community at large, and get some quick, direct help for any Zig related problem.
+- [#zig][irc] on irc.freenode.net is the main Zig IRC channel.
+- [/r/Zig][reddit] is the main Zig subreddit.
+- [Stack Overflow][stack-overflow] can be used to discover code snippets and solutions to problems that may have already asked and maybe solved by others.
+
+[discord]: https://discordapp.com
+[discord-zig]: https://discord.com/invite/gxsFFjE
+[documentation]: https://ziglang.org/documentation/master
+[irc]: https://webchat.freenode.net/?channels=%23zig
+[reddit]: https://www.reddit.com/r/Zig
+[stack-overflow]: https://stackoverflow.com/questions/tagged/zig
+[zig-learn]: https://ziglearn.org/
+[ziglings]: https://github.com/ratfactor/ziglings

zig/collatz-conjecture/README.md

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+# Collatz Conjecture
+
+Welcome to Collatz Conjecture on Exercism's Zig Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+The Collatz Conjecture or 3x+1 problem can be summarized as follows:
+
+Take any positive integer n.
+If n is even, divide n by 2 to get n / 2.
+If n is odd, multiply n by 3 and add 1 to get 3n + 1.
+Repeat the process indefinitely.
+The conjecture states that no matter which number you start with, you will always reach 1 eventually.
+
+Given a number n, return the number of steps required to reach 1.
+
+## Examples
+
+Starting with n = 12, the steps would be as follows:
+
+0. 12
+1. 6
+2. 3
+3. 10
+4. 5
+5. 16
+6. 8
+7. 4
+8. 2
+9. 1
+
+Resulting in 9 steps.
+So for input n = 12, the return value would be 9.
+
+## Source
+
+### Created by
+
+- @massivelivefun
+
+### Contributed to by
+
+- @ee7
+
+### Based on
+
+An unsolved problem in mathematics named after mathematician Lothar Collatz - https://en.wikipedia.org/wiki/3x_%2B_1_problem

zig/collatz-conjecture/collatz_conjecture.zig

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+pub const ComputationError = error {
+    IllegalArgument
+};
+
+pub fn steps(number: usize) anyerror!usize {
+    if (number < 1) {
+        return ComputationError.IllegalArgument;
+    }
+
+    var count: usize = 0;
+    var curNum: usize = number;
+    while(curNum != 1) {
+        count += 1;
+        if (curNum % 2 == 0) {
+            curNum = curNum / 2;
+        } else {
+            curNum = curNum * 3 + 1;
+        }
+    }
+
+    return count;
+}

zig/collatz-conjecture/test_collatz_conjecture.zig

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+const std = @import("std");
+const testing = std.testing;
+
+const collatz_conjecture = @import("collatz_conjecture.zig");
+const ComputationError = collatz_conjecture.ComputationError;
+
+test "zero steps for one" {
+    const expected: usize = 0;
+    const actual = try collatz_conjecture.steps(1);
+    try testing.expectEqual(expected, actual);
+}
+
+test "divide if even" {
+    const expected: usize = 4;
+    const actual = try collatz_conjecture.steps(16);
+    try testing.expectEqual(expected, actual);
+}
+
+test "even and odd steps" {
+    const expected: usize = 9;
+    const actual = try collatz_conjecture.steps(12);
+    try testing.expectEqual(expected, actual);
+}
+
+test "large number of even and odd steps" {
+    const expected: usize = 152;
+    const actual = try collatz_conjecture.steps(1_000_000);
+    try testing.expectEqual(expected, actual);
+}
+
+test "zero is an error" {
+    const expected = ComputationError.IllegalArgument;
+    const actual = collatz_conjecture.steps(0);
+    try testing.expectError(expected, actual);
+}