Add rectangles exercise

config.json

@@ -282,6 +282,14 @@
         "prerequisites": [],
         "difficulty": 6
       },
+      {
+        "slug": "rectangles",
+        "name": "Rectangles",
+        "uuid": "d06c5066-917e-454c-8549-3af3e8f7bd9f",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 8
+      },
       {
         "slug": "zebra-puzzle",
         "name": "Zebra Puzzle",

exercises/practice/rectangles/.docs/instructions.md

@@ -0,0 +1,63 @@
+# Instructions
+
+Count the rectangles in an ASCII diagram like the one below.
+
+```text
+   +--+
+  ++  |
++-++--+
+|  |  |
++--+--+
+```
+
+The above diagram contains these 6 rectangles:
+
+```text
+
+
++-----+
+|     |
++-----+
+```
+
+```text
+   +--+
+   |  |
+   |  |
+   |  |
+   +--+
+```
+
+```text
+   +--+
+   |  |
+   +--+
+
+
+```
+
+```text
+
+
+   +--+
+   |  |
+   +--+
+```
+
+```text
+
+
++--+
+|  |
++--+
+```
+
+```text
+
+  ++
+  ++
+
+
+```
+
+You may assume that the input is always a proper rectangle (i.e. the length of every line equals the length of the first line).

exercises/practice/rectangles/.meta/config.json

@@ -0,0 +1,17 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "rectangles.s"
+    ],
+    "test": [
+      "rectangles_test.c"
+    ],
+    "example": [
+      ".meta/example.s"
+    ]
+  },
+  "blurb": "Count the rectangles in an ASCII diagram."
+}

exercises/practice/rectangles/.meta/example.s

@@ -0,0 +1,85 @@
+.text
+.globl rectangles
+
+/* int rectangles(const char **strings); */
+rectangles:
+        mov     x1, x0
+        mov     x0, xzr                 /* initialize count */
+
+.top_row:
+        ldr     x2, [x1], #8            /* address of start of row */
+        cbz     x2, .return
+
+        mov     x3, x2                  /* pointer into row */
+
+.left_column:
+        ldrb    w4, [x3], #1            /* load byte, post-increment */
+        cbz     w4, .top_row
+
+        cmp     w4, #'+'
+        bne     .left_column
+
+        mov     x4, x3
+
+.right_column:
+        ldrb    w5, [x4], #1            /* load byte, post-increment */
+        cmp     w5, #'-'
+        beq     .right_column
+
+        cmp     w5, #'+'
+        bne     .left_column
+
+        sub     x5, x3, x2
+        sub     x5, x5, #1              /* offset of left column from start of row */
+        sub     x6, x4, x2
+        sub     x6, x6, #1              /* offset of right column from start of row */
+        mov     x7, x1
+
+.bottom_row:
+        ldr     x8, [x7], #8            /* address of start of row */
+        cbz     x8, .right_column
+
+        mov     w11, wzr                /* number of | (0, 1 or 2) */
+        mov     w12, wzr                /* number of + (0, 1 or 2) */
+
+        ldrb    w9, [x8, x5]
+        cmp     w9, #'|'
+        cinc    w11, w11, eq
+        cmp     w9, #'+'
+        cinc    w12, w12, eq
+
+        ldrb    w9, [x8, x6]
+        cmp     w9, #'|'
+        cinc    w11, w11, eq
+        cmp     w9, #'+'
+        cinc    w12, w12, eq
+
+        add     w11, w11, w12           /* number of | or + (0, 1 or 2) */
+        cmp     w11, #2
+        bne    .right_column
+
+        cmp w12, #2
+        bne    .bottom_row
+
+        mov     x11, x5                 /* index into bottom row */
+
+.scan_bottom:
+        add     x11, x11, #1
+        cmp     x11, x6
+        beq     .accept
+
+        ldrb    w9, [x8, x11]
+        cmp     w9, #'-'
+        beq     .scan_bottom
+
+        cmp     w9, #'+'
+        beq     .scan_bottom
+
+        b       .bottom_row
+
+.accept:
+        add     x0, x0, #1
+        b       .bottom_row
+
+.return:
+        ret

exercises/practice/rectangles/.meta/tests.toml

@@ -0,0 +1,52 @@
+# 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.
+
+[485b7bab-4150-40aa-a8db-73013427d08c]
+description = "no rows"
+
+[076929ed-27e8-45dc-b14b-08279944dc49]
+description = "no columns"
+
+[0a8abbd1-a0a4-4180-aa4e-65c1b1a073fa]
+description = "no rectangles"
+
+[a4ba42e9-4e7f-4973-b7c7-4ce0760ac6cd]
+description = "one rectangle"
+
+[ced06550-83da-4d23-98b7-d24152e0db93]
+description = "two rectangles without shared parts"
+
+[5942d69a-a07c-41c8-8b93-2d13877c706a]
+description = "five rectangles with shared parts"
+
+[82d70be4-ab37-4bf2-a433-e33778d3bbf1]
+description = "rectangle of height 1 is counted"
+
+[57f1bc0e-2782-401e-ab12-7c01d8bfc2e0]
+description = "rectangle of width 1 is counted"
+
+[ef0bb65c-bd80-4561-9535-efc4067054f9]
+description = "1x1 square is counted"
+
+[e1e1d444-e926-4d30-9bf3-7d8ec9a9e330]
+description = "only complete rectangles are counted"
+
+[ca021a84-1281-4a56-9b9b-af14113933a4]
+description = "rectangles can be of different sizes"
+
+[51f689a7-ef3f-41ae-aa2f-5ea09ad897ff]
+description = "corner is required for a rectangle to be complete"
+
+[d78fe379-8c1b-4d3c-bdf7-29bfb6f6dc66]
+description = "large input with many rectangles"
+
+[6ef24e0f-d191-46da-b929-4faca24b4cd2]
+description = "rectangles must have four sides"

exercises/practice/rectangles/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/rectangles/rectangles.s

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