Add run-length-encoding exercise (#130)

config.json

@@ -386,6 +386,14 @@
         "prerequisites": [],
         "difficulty": 5
       },
+      {
+        "slug": "run-length-encoding",
+        "name": "Run-Length Encoding",
+        "uuid": "e2cb9eb9-c1fd-44a9-a7fa-ac8199d1680d",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "sieve",
         "name": "Sieve",

exercises/practice/affine-cipher/affine_cipher_test.c

@@ -3,7 +3,6 @@
 #define BUFFER_SIZE 80
 
 extern void encode(char *buffer, const char *phrase, unsigned a, unsigned b);
-
 extern void decode(char *buffer, const char *phrase, unsigned a, unsigned b);
 
 void setUp(void) {

exercises/practice/atbash-cipher/atbash_cipher_test.c

@@ -3,7 +3,6 @@
 #define BUFFER_SIZE 80
 
 extern void encode(char *buffer, const char *phrase);
-
 extern void decode(char *buffer, const char *phrase);
 
 void setUp(void) {

exercises/practice/difference-of-squares/difference_of_squares_test.c

@@ -3,9 +3,7 @@
 #include <stdint.h>
 
 extern uint64_t square_of_sum(uint64_t number);
-
 extern uint64_t sum_of_squares(uint64_t number);
-
 extern uint64_t difference_of_squares(uint64_t number);
 
 void setUp(void) {

exercises/practice/pig-latin/pig_latin_test.c

@@ -89,6 +89,14 @@ void test_word_beginning_with_q_without_a_following_u(void) {
     TEST_ASSERT_EQUAL_STRING("atqay", buffer);
 }
 
+void test_word_beginning_with_consonant_and_vowel_containing_qu(void) {
+    TEST_IGNORE();
+    char buffer[BUFFER_SIZE];
+
+    translate(buffer, "liquid");
+    TEST_ASSERT_EQUAL_STRING("iquidlay", buffer);
+}
+
 void test_word_beginning_with_ch(void) {
     TEST_IGNORE();
     char buffer[BUFFER_SIZE];
@@ -197,6 +205,7 @@ int main(void) {
     RUN_TEST(test_word_beginning_with_k);
     RUN_TEST(test_word_beginning_with_x);
     RUN_TEST(test_word_beginning_with_q_without_a_following_u);
+    RUN_TEST(test_word_beginning_with_consonant_and_vowel_containing_qu);
     RUN_TEST(test_word_beginning_with_ch);
     RUN_TEST(test_word_beginning_with_qu);
     RUN_TEST(test_word_beginning_with_qu_and_a_preceding_consonant);

exercises/practice/run-length-encoding/.docs/instructions.md

@@ -0,0 +1,20 @@
+# Instructions
+
+Implement run-length encoding and decoding.
+
+Run-length encoding (RLE) is a simple form of data compression, where runs (consecutive data elements) are replaced by just one data value and count.
+
+For example we can represent the original 53 characters with only 13.
+
+```text
+"WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWB"  ->  "12WB12W3B24WB"
+```
+
+RLE allows the original data to be perfectly reconstructed from the compressed data, which makes it a lossless data compression.
+
+```text
+"AABCCCDEEEE"  ->  "2AB3CD4E"  ->  "AABCCCDEEEE"
+```
+
+For simplicity, you can assume that the unencoded string will only contain the letters A through Z (either lower or upper case) and whitespace.
+This way data to be encoded will never contain any numbers and numbers inside data to be decoded always represent the count for the following character.

exercises/practice/run-length-encoding/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "run_length_encoding.s"
+    ],
+    "test": [
+      "run_length_encoding_test.c"
+    ],
+    "example": [
+      ".meta/example.s"
+    ]
+  },
+  "blurb": "Implement run-length encoding and decoding.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Run-length_encoding"
+}

exercises/practice/run-length-encoding/.meta/example.s

@@ -0,0 +1,83 @@
+.text
+.globl encode
+.globl decode
+
+/* extern void encode(char *buffer, const char *string); */
+encode:
+        mov     w10, #10
+
+.encode_next:
+        mov     x2, x1                  /* address at start of run */
+        ldrb    w3, [x1], #1            /* read byte, post-increment */
+        cbz     w3, terminate
+
+.encode_read:
+        ldrb    w4, [x1], #1            /* read byte, post-increment */
+        cmp     w4, w3
+        beq     .encode_read
+
+        sub     x1, x1, #1              /* address of first byte after run */
+        mov     x4, x0
+        sub     x2, x1, x2              /* length of run */
+        cmp     x2, #1
+        beq     .encode_write
+
+.encode_digit:
+        udiv    w5, w2, w10              /* quotient */
+        msub    w6, w5, w10, w2          /* remainder */
+        mov     w2, w5
+        add     w6, w6, #'0'
+        strb    w6, [x0], #1
+        cbnz    w2, .encode_digit
+
+        mov     x5, x0
+
+.encode_reverse:
+        sub     x5, x5, #1
+        cmp     x5, x4
+        beq     .encode_write           /* middle byte of odd length string */
+
+        ldrb    w6, [x5]
+        ldrb    w7, [x4]
+        strb    w6, [x4], #1            /* store byte, post-increment */
+        strb    w7, [x5]
+        cmp     x5, x4
+        bne     .encode_reverse
+                                        /* middle bytes of even length string */
+
+.encode_write:
+        strb    w3, [x0], #1
+        b       .encode_next
+
+terminate:
+        strb    wzr, [x0]
+        ret
+
+/* extern void decode(char *buffer, const char *string); */
+decode:
+        mov     w10, #10
+
+.decode_next:
+        mov     w2, wzr                 /* count */
+
+.decode_read:
+        ldrb    w3, [x1], #1            /* read byte, post-increment */
+        cbz     w3, terminate
+
+        sub     w4, w3, #'0'
+        cmp     w4, w10
+        blo     .decode_digit
+
+        cmp     w2, wzr
+        cinc    w2, w2, eq
+
+.decode_write:
+        strb    w3, [x0], #1            /* write byte, post-increment */
+        sub     w2, w2, #1
+        cbnz    w2, .decode_write
+
+        b       .decode_next
+
+.decode_digit:
+        madd    w2, w2, w10, w4
+        b       .decode_read

exercises/practice/run-length-encoding/.meta/tests.toml

@@ -0,0 +1,49 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[ad53b61b-6ffc-422f-81a6-61f7df92a231]
+description = "run-length encode a string -> empty string"
+
+[52012823-b7e6-4277-893c-5b96d42f82de]
+description = "run-length encode a string -> single characters only are encoded without count"
+
+[b7868492-7e3a-415f-8da3-d88f51f80409]
+description = "run-length encode a string -> string with no single characters"
+
+[859b822b-6e9f-44d6-9c46-6091ee6ae358]
+description = "run-length encode a string -> single characters mixed with repeated characters"
+
+[1b34de62-e152-47be-bc88-469746df63b3]
+description = "run-length encode a string -> multiple whitespace mixed in string"
+
+[abf176e2-3fbd-40ad-bb2f-2dd6d4df721a]
+description = "run-length encode a string -> lowercase characters"
+
+[7ec5c390-f03c-4acf-ac29-5f65861cdeb5]
+description = "run-length decode a string -> empty string"
+
+[ad23f455-1ac2-4b0e-87d0-b85b10696098]
+description = "run-length decode a string -> single characters only"
+
+[21e37583-5a20-4a0e-826c-3dee2c375f54]
+description = "run-length decode a string -> string with no single characters"
+
+[1389ad09-c3a8-4813-9324-99363fba429c]
+description = "run-length decode a string -> single characters with repeated characters"
+
+[3f8e3c51-6aca-4670-b86c-a213bf4706b0]
+description = "run-length decode a string -> multiple whitespace mixed in string"
+
+[29f721de-9aad-435f-ba37-7662df4fb551]
+description = "run-length decode a string -> lowercase string"
+
+[2a762efd-8695-4e04-b0d6-9736899fbc16]
+description = "encode and then decode -> encode followed by decode gives original string"

exercises/practice/run-length-encoding/Makefile

@@ -0,0 +1,36 @@
+AS = aarch64-linux-gnu-as
+CC = aarch64-linux-gnu-gcc
+
+CFLAGS = -g -Wall -Wextra -pedantic -Werror
+LDFLAGS =
+
+ALL_LDFLAGS = -pie -Wl,--fatal-warnings
+
+ALL_CFLAGS = -std=c99 -fPIE $(CFLAGS)
+ALL_LDFLAGS += $(LDFLAGS)
+
+C_OBJS = $(patsubst %.c,%.o,$(wildcard *.c))
+AS_OBJS = $(patsubst %.s,%.o,$(wildcard *.s))
+ALL_OBJS = $(filter-out example.o,$(C_OBJS) $(AS_OBJS) vendor/unity.o)
+
+CC_CMD = $(CC) $(ALL_CFLAGS) -c -o $@ $<
+
+all: tests
+	qemu-aarch64 -L /usr/aarch64-linux-gnu ./$<
+
+tests: $(ALL_OBJS)
+	@$(CC) $(ALL_CFLAGS) $(ALL_LDFLAGS) -o $@ $(ALL_OBJS)
+
+%.o: %.s
+	@$(AS) -o $@ $<
+
+%.o: %.c
+	@$(CC_CMD)
+
+vendor/unity.o: vendor/unity.c vendor/unity.h vendor/unity_internals.h
+	@$(CC_CMD)
+
+clean:
+	@rm -f *.o vendor/*.o tests
+
+.PHONY: all clean

exercises/practice/run-length-encoding/run_length_encoding.s

@@ -0,0 +1,9 @@
+.text
+.globl encode
+.globl decode
+
+encode:
+    ret
+
+decode:
+    ret