Add dominoes exercise

config.json

@@ -506,6 +506,14 @@
         "prerequisites": [],
         "difficulty": 8
       },
+      {
+        "slug": "dominoes",
+        "name": "Dominoes",
+        "uuid": "58b0fc1e-db18-4b0b-bf31-058d8e6eb753",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 9
+      },
       {
         "slug": "zebra-puzzle",
         "name": "Zebra Puzzle",

exercises/practice/dominoes/.docs/instructions.md

@@ -0,0 +1,15 @@
+# Instructions
+
+Make a chain of dominoes.
+
+Compute a way to order a given set of domino stones so that they form a correct domino chain.
+In the chain, the dots on one half of a stone must match the dots on the neighboring half of an adjacent stone.
+Additionally, the dots on the halves of the stones without neighbors (the first and last stone) must match each other.
+
+For example given the stones `[2|1]`, `[2|3]` and `[1|3]` you should compute something
+like `[1|2] [2|3] [3|1]` or `[3|2] [2|1] [1|3]` or `[1|3] [3|2] [2|1]` etc, where the first and last numbers are the same.
+
+For stones `[1|2]`, `[4|1]` and `[2|3]` the resulting chain is not valid: `[4|1] [1|2] [2|3]`'s first and last numbers are not the same.
+4 != 3
+
+Some test cases may use duplicate stones in a chain solution, assume that multiple Domino sets are being used.

exercises/practice/dominoes/.docs/introduction.md

@@ -0,0 +1,13 @@
+# Introduction
+
+In Toyland, the trains are always busy delivering treasures across the city, from shiny marbles to rare building blocks.
+The tracks they run on are made of colorful domino-shaped pieces, each marked with two numbers.
+For the trains to move, the dominoes must form a perfect chain where the numbers match.
+
+Today, an urgent delivery of rare toys is on hold.
+You've been handed a set of track pieces to inspect.
+If they can form a continuous chain, the train will be on its way, bringing smiles across Toyland.
+If not, the set will be discarded, and another will be tried.
+
+The toys are counting on you to solve this puzzle.
+Will the dominoes connect the tracks and send the train rolling, or will the set be left behind?

exercises/practice/dominoes/.meta/config.json

@@ -0,0 +1,17 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "dominoes.s"
+    ],
+    "test": [
+      "dominoes_test.c"
+    ],
+    "example": [
+      ".meta/example.s"
+    ]
+  },
+  "blurb": "Make a chain of dominoes."
+}

exercises/practice/dominoes/.meta/example.s

@@ -0,0 +1,89 @@
+.text
+.globl can_chain
+
+/* int root(int number, void*, uint8_t *table); */
+root:
+        mov     w9, w0
+        ldrb    w0, [x2, x0]
+        cmp     w0, w9
+        bne     root
+
+        ret
+
+/* void merge(size_t domino_count, const domino_t *dominoes, uint8_t *table); */
+merge:
+        mov     x14, lr                 /* preserve return address */
+        lsl     w10, w0, #2             /* number of bytes occupied by dominoes array */
+
+.merge_loop:
+        sub     w10, w10, #2
+        ldrh    w0, [x1, x10]           /* number on domino half */
+        bl      root
+        mov     w11, w0
+
+        sub     w10, w10, #2
+        ldrh    w0, [x1, x10]            /* number on domino half */
+        bl      root
+
+        strb    w0, [x2, x11]           /* link domino halves in table */
+
+        cbnz    w10, .merge_loop
+
+        ret     x14
+
+/* extern int can_chain(size_t domino_count, const domino_t *dominoes); */
+can_chain:
+        stp     xzr, xzr, [sp, #-16]!
+        mov     x15, lr                 /* preserve return address */
+        cmp     w0, wzr
+        beq     .accept
+
+        mov     x2, sp
+        lsl     w9, w0, #2              /* number of bytes occupied by dominoes array */
+
+.count_numbers:
+        sub     w9, w9, #2
+        ldrh    w10, [x1, x9]           /* number on domino half */
+        ldrb    w11, [x2, x10]
+        add     w11, w11, #1            /* increment tally */
+        strb    w11, [x2, x10]
+        cbnz    w9, .count_numbers
+
+        mov     w9, #16
+        mov     w14, #255
+
+.parity:
+        sub     w9, w9, #1
+        ldrb    w10, [sp, x9]
+        tst     w10, #1                 /* check if number appears an odd number of times */
+        bne     .reject
+
+        tst     w10, w10
+        csel    w11, w14, w9, eq
+        strb    w11, [sp, x9]           /* populate disjoint set (union find) array */
+        cbnz    w9, .parity
+
+        bl      merge
+
+        mov     w9, #16
+        mov     w11, wzr
+
+.count_roots:
+        sub     w9, w9, #1
+        ldrb    w10, [x2, x9]
+        cmp     w10, w9
+        cinc    w11, w11, eq
+        cbnz    w9, .count_roots
+
+        cmp     w11, #1
+        bne     .reject
+
+.accept:
+        mov     w0, #1
+        add     sp, sp, #16             /* restore stack pointer */
+        ret     x15
+
+.reject:
+        mov     w0, wzr
+        add     sp, sp, #16             /* restore stack pointer */
+        ret     x15

exercises/practice/dominoes/.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.
+
+[31a673f2-5e54-49fe-bd79-1c1dae476c9c]
+description = "empty input = empty output"
+
+[4f99b933-367b-404b-8c6d-36d5923ee476]
+description = "singleton input = singleton output"
+
+[91122d10-5ec7-47cb-b759-033756375869]
+description = "singleton that can't be chained"
+
+[be8bc26b-fd3d-440b-8e9f-d698a0623be3]
+description = "three elements"
+
+[99e615c6-c059-401c-9e87-ad7af11fea5c]
+description = "can reverse dominoes"
+
+[51f0c291-5d43-40c5-b316-0429069528c9]
+description = "can't be chained"
+
+[9a75e078-a025-4c23-8c3a-238553657f39]
+description = "disconnected - simple"
+
+[0da0c7fe-d492-445d-b9ef-1f111f07a301]
+description = "disconnected - double loop"
+
+[b6087ff0-f555-4ea0-a71c-f9d707c5994a]
+description = "disconnected - single isolated"
+
+[2174fbdc-8b48-4bac-9914-8090d06ef978]
+description = "need backtrack"
+
+[167bb480-dfd1-4318-a20d-4f90adb4a09f]
+description = "separate loops"
+
+[cd061538-6046-45a7-ace9-6708fe8f6504]
+description = "nine elements"
+
+[44704c7c-3adb-4d98-bd30-f45527cf8b49]
+description = "separate three-domino loops"

exercises/practice/dominoes/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/dominoes/dominoes.s

@@ -0,0 +1,5 @@
+.text
+.globl can_chain
+
+can_chain:
+    ret

exercises/practice/dominoes/dominoes_test.c

@@ -0,0 +1,113 @@
+#include "vendor/unity.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
+typedef struct {
+    uint16_t first;
+    uint16_t second;
+} domino_t;
+
+extern int can_chain(size_t domino_count, const domino_t *dominoes);
+
+void setUp(void) {
+}
+
+void tearDown(void) {
+}
+
+void test_empty_input__empty_output(void) {
+    TEST_ASSERT_TRUE(can_chain(0, NULL));
+}
+
+void test_singleton_input__singleton_output(void) {
+    TEST_IGNORE();
+    const domino_t dominoes[] = {{1, 1}};
+    TEST_ASSERT_TRUE(can_chain(ARRAY_SIZE(dominoes), dominoes));
+}
+
+void test_singleton_that_cant_be_chained(void) {
+    TEST_IGNORE();
+    const domino_t dominoes[] = {{1, 2}};
+    TEST_ASSERT_FALSE(can_chain(ARRAY_SIZE(dominoes), dominoes));
+}
+
+void test_three_elements(void) {
+    TEST_IGNORE();
+    const domino_t dominoes[] = {{1, 2}, {3, 1}, {2, 3}};
+    TEST_ASSERT_TRUE(can_chain(ARRAY_SIZE(dominoes), dominoes));
+}
+
+void test_can_reverse_dominoes(void) {
+    TEST_IGNORE();
+    const domino_t dominoes[] = {{1, 2}, {1, 3}, {2, 3}};
+    TEST_ASSERT_TRUE(can_chain(ARRAY_SIZE(dominoes), dominoes));
+}
+
+void test_cant_be_chained(void) {
+    TEST_IGNORE();
+    const domino_t dominoes[] = {{1, 2}, {4, 1}, {2, 3}};
+    TEST_ASSERT_FALSE(can_chain(ARRAY_SIZE(dominoes), dominoes));
+}
+
+void test_disconnected__simple(void) {
+    TEST_IGNORE();
+    const domino_t dominoes[] = {{1, 1}, {2, 2}};
+    TEST_ASSERT_FALSE(can_chain(ARRAY_SIZE(dominoes), dominoes));
+}
+
+void test_disconnected__double_loop(void) {
+    TEST_IGNORE();
+    const domino_t dominoes[] = {{1, 2}, {2, 1}, {3, 4}, {4, 3}};
+    TEST_ASSERT_FALSE(can_chain(ARRAY_SIZE(dominoes), dominoes));
+}
+
+void test_disconnected__single_isolated(void) {
+    TEST_IGNORE();
+    const domino_t dominoes[] = {{1, 2}, {2, 3}, {3, 1}, {4, 4}};
+    TEST_ASSERT_FALSE(can_chain(ARRAY_SIZE(dominoes), dominoes));
+}
+
+void test_need_backtrack(void) {
+    TEST_IGNORE();
+    const domino_t dominoes[] = {{1, 2}, {2, 3}, {3, 1}, {2, 4}, {2, 4}};
+    TEST_ASSERT_TRUE(can_chain(ARRAY_SIZE(dominoes), dominoes));
+}
+
+void test_separate_loops(void) {
+    TEST_IGNORE();
+    const domino_t dominoes[] = {{1, 2}, {2, 3}, {3, 1}, {1, 1}, {2, 2}, {3, 3}};
+    TEST_ASSERT_TRUE(can_chain(ARRAY_SIZE(dominoes), dominoes));
+}
+
+void test_nine_elements(void) {
+    TEST_IGNORE();
+    const domino_t dominoes[] = {{1, 2}, {5, 3}, {3, 1}, {1, 2}, {2, 4}, {1, 6}, {2, 3}, {3, 4}, {5, 6}};
+    TEST_ASSERT_TRUE(can_chain(ARRAY_SIZE(dominoes), dominoes));
+}
+
+void test_separate_threedomino_loops(void) {
+    TEST_IGNORE();
+    const domino_t dominoes[] = {{1, 2}, {2, 3}, {3, 1}, {4, 5}, {5, 6}, {6, 4}};
+    TEST_ASSERT_FALSE(can_chain(ARRAY_SIZE(dominoes), dominoes));
+}
+
+int main(void) {
+    UNITY_BEGIN();
+    RUN_TEST(test_empty_input__empty_output);
+    RUN_TEST(test_singleton_input__singleton_output);
+    RUN_TEST(test_singleton_that_cant_be_chained);
+    RUN_TEST(test_three_elements);
+    RUN_TEST(test_can_reverse_dominoes);
+    RUN_TEST(test_cant_be_chained);
+    RUN_TEST(test_disconnected__simple);
+    RUN_TEST(test_disconnected__double_loop);
+    RUN_TEST(test_disconnected__single_isolated);
+    RUN_TEST(test_need_backtrack);
+    RUN_TEST(test_separate_loops);
+    RUN_TEST(test_nine_elements);
+    RUN_TEST(test_separate_threedomino_loops);
+    return UNITY_END();
+}