add exercise for hamming

exercises/hamming/.exercism/config.json

+{
+  "authors": [
+    "sunzenshen"
+  ],
+  "contributors": [
+    "bcc32",
+    "Gamecock",
+    "gea-migration",
+    "h-3-0",
+    "hintjens",
+    "JacobMikkelsen",
+    "kytrinyx",
+    "lpil",
+    "patricksjackson",
+    "QLaille",
+    "RealBarrettBrown",
+    "ryanplusplus",
+    "siebenschlaefer",
+    "sjwarner",
+    "wolf99"
+  ],
+  "files": {
+    "solution": [
+      "hamming.c",
+      "hamming.h"
+    ],
+    "test": [
+      "test_hamming.c"
+    ],
+    "example": [
+      ".meta/example.c",
+      ".meta/example.h"
+    ]
+  },
+  "blurb": "Calculate the Hamming difference between two DNA strands.",
+  "source": "The Calculating Point Mutations problem at Rosalind",
+  "source_url": "http://rosalind.info/problems/hamm/"
+}

exercises/hamming/.exercism/metadata.json

+{"track":"c","exercise":"hamming","id":"355be382464849cea1bb20968f94c910","url":"https://exercism.org/tracks/c/exercises/hamming","handle":"mactavishz","is_requester":true,"auto_approve":false}
\ No newline at end of file

exercises/hamming/HELP.md

+# Help
+
+## Running the tests
+
+Get the first test compiling, linking and passing by following the [three rules of test-driven development][3-tdd-rules].
+
+The included makefile can be used to create and run the tests using the `test` task.
+
+```console
+$ make test
+```
+
+Create just the functions you need to satisfy any compiler errors and get the test to fail.
+Then write just enough code to get the test to pass.
+Once you've done that, move onto the next test.
+
+As you progress through the tests, take the time to refactor your implementation for readability and expressiveness and then go on to the next test.
+
+Try to use standard C99 facilities in preference to writing your own low-level algorithms or facilities by hand.
+
+[3-tdd-rules]: https://blog.cleancoder.com/uncle-bob/2014/12/17/TheCyclesOfTDD.html
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit hamming.c hamming.h` 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 [C track's documentation](https://exercism.org/docs/tracks/c)
+- [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.
+
+Make sure you have read the [C track-specific documentation][c-track] on the Exercism site.
+This covers the basic information on setting up the development environment expected by the exercises.
+
+## Submitting Incomplete Solutions
+
+If you are struggling with a particular exercise, it is possible to submit an incomplete solution so you can see how others have completed the exercise.
+
+## Resources
+
+To get help if having trouble, you can use the following resources:
+
+- [StackOverflow][] can be used to search for your problem and see if it has been answered already. You can also ask and answer questions.
+- [CPPReference][] can be used to look up information on C concepts, operators, types, standard library functions and more.
+- [TutorialsPoint][] has similar content as CPPReference in its C programming section.
+- [The C Programming][K&R] book by K&R is the original source of the language and is still useful today.
+
+[c-track]: https://exercism.org/docs/tracks/c
+[stackoverflow]: http://stackoverflow.com/questions/tagged/c
+[cppreference]: https://en.cppreference.com/w/c
+[tutorialspoint]: https://www.tutorialspoint.com/cprogramming/
+[K&R]: https://www.amazon.com/Programming-Language-2nd-Brian-Kernighan/dp/0131103628/
\ No newline at end of file

exercises/hamming/README.md

+# Hamming
+
+Here is a small exercise that helps you understand pointer arithmetic and String in C.
+
+## Instructions
+
+Calculate the Hamming Distance between two DNA sequences.
+
+If we compare two sequences of DNA and count the differences between them we can see how many mismatches occurred.
+
+This is known as the "Hamming Distance".
+
+We read DNA using the letters C,A,G and T. Two sequences might look like this:
+
+```
+GAGCCTACTAACGGGAT
+CATCGTAATGACGGCCT
+^ ^ ^  ^ ^    ^^
+```
+
+They have 7 differences, and therefore the Hamming Distance is 7.
+
+## Implementation notes
+
+The Hamming distance is only defined for sequences of equal length, so an attempt to calculate it between sequences of different lengths should not work.
+
+## Tips
+
+You could use auxiliary functions such as `strlen` to get the length of a given string. These functions are defined in `<string.h>`
+
+## Testing
+
+The included makefile can be used to create and run the tests using the following commands:
+
+```bash
+# run unit tests
+make test
+
+# check memory leaks
+make memcheck
+
+# clean all compilation files
+make clean
+```
+
+## Credit
+
+Adapted from [here](https://github.com/exercism/c/tree/main/exercises/practice/hamming)

exercises/hamming/hamming.c

+#include "hamming.h"
+
+int compute(const char *lhs, const char *rhs) {
+    // TODO: implement this fucntion
+}

exercises/hamming/hamming.h

+#ifndef HAMMING_H
+#define HAMMING_H
+
+int compute(const char *lhs, const char *rhs);
+
+#endif

exercises/hamming/makefile

+### If you wish to use extra libraries (math.h for instance),
+### add their flags here (-lm in our case) in the "LIBS" variable.
+
+LIBS = -lm
+
+###
+CFLAGS  = -std=c99
+CFLAGS += -g
+CFLAGS += -Wall
+CFLAGS += -Wextra
+CFLAGS += -pedantic
+CFLAGS += -Wmissing-declarations
+CFLAGS += -DUNITY_SUPPORT_64 -DUNITY_OUTPUT_COLOR
+
+ASANFLAGS  = -fsanitize=address
+ASANFLAGS += -fno-common
+ASANFLAGS += -fno-omit-frame-pointer
+
+.PHONY: test
+test: tests.out
+	@./tests.out
+
+.PHONY: memcheck
+memcheck: ./*.c ./*.h
+	@echo Compiling $@
+	@$(CC) $(ASANFLAGS) $(CFLAGS) ../unity/unity.c ./*.c -o memcheck.out $(LIBS)
+	@./memcheck.out
+	@echo "Memory check passed"
+
+.PHONY: clean
+clean:
+	rm -rf *.o *.out *.out.dSYM
+
+tests.out: ./*.c ./*.h
+	@echo Compiling $@
+	@$(CC) $(CFLAGS) ../unity/unity.c ./*.c -o tests.out $(LIBS)

exercises/hamming/test_hamming.c

+#include "../unity/unity.h"
+#include "hamming.h"
+
+void setUp(void) {}
+
+void tearDown(void) {}
+
+static void test_empty_strands(void) { TEST_ASSERT_EQUAL(0, compute("", "")); }
+
+static void test_single_identical_strands(void) {
+  TEST_ASSERT_EQUAL(0, compute("A", "A"));
+}
+
+static void test_single_letter_different_strands(void) {
+  TEST_ASSERT_EQUAL(1, compute("G", "T"));
+}
+
+static void test_long_identical_strands(void) {
+  TEST_ASSERT_EQUAL(0, compute("GGACTGAAATCTG", "GGACTGAAATCTG"));
+}
+
+static void test_long_different_strands(void) {
+  TEST_ASSERT_EQUAL(9, compute("GGACGGATTCTG", "AGGACGGATTCT"));
+}
+
+static void test_disallow_first_strand_when_longer(void) {
+  TEST_ASSERT_EQUAL(-1, compute("AATG", "AAA"));
+}
+
+static void test_disallow_second_strand_when_longer(void) {
+  TEST_ASSERT_EQUAL(-1, compute("ATA", "AGTG"));
+}
+
+static void test_disallow_empty_first_strand(void) {
+  TEST_ASSERT_EQUAL(-1, compute("", "G"));
+}
+
+static void test_disallow_empty_second_strand(void) {
+  TEST_ASSERT_EQUAL(-1, compute("G", ""));
+}
+
+int main(void) {
+  UnityBegin("test_hamming.c");
+
+  RUN_TEST(test_empty_strands);
+  RUN_TEST(test_single_identical_strands);
+  RUN_TEST(test_single_letter_different_strands);
+  RUN_TEST(test_long_identical_strands);
+  RUN_TEST(test_long_different_strands);
+  RUN_TEST(test_disallow_first_strand_when_longer);
+  RUN_TEST(test_disallow_second_strand_when_longer);
+  RUN_TEST(test_disallow_empty_first_strand);
+  RUN_TEST(test_disallow_empty_second_strand);
+
+  return UnityEnd();
+}