Aoc days 9, 10, 11

.gitignore

@@ -25,11 +25,12 @@
 # ide stuff
 /.vscode/
 
-# Advent of Code input files https://adventofcode.com/
-# These are large text files, and each AoC user gets different input files.
-# Tests use sampleinput.txt files, copied from problem descriptions
+# Advent of Code files https://adventofcode.com/
+# Inputs are large text files, and each AoC user gets different input files.
+# Tests use sampleinput.txt files, copied from problem descriptions.
+#
+# Creator of AoC tells people not to commit inputs to git. I also cannot
+# commit problem descriptions to cit because of copyright.
+/examples/aoc2023/day*/input
 /examples/aoc2023/day*/input.txt
-
-# files created by https://github.com/scarvalhojr/aoc-cli
-# not sure if I can commit these to git because copyright
 /examples/aoc2023/day*/puzzle.md

examples/aoc2023/day09/part1.jou

@@ -0,0 +1,48 @@
+import "stdlib/io.jou"
+import "stdlib/ascii.jou"
+import "stdlib/str.jou"
+import "stdlib/mem.jou"
+
+
+def predict_next(nums: long*, len: int) -> long:
+    all_zero = True
+    for i = 0; i < len; i++:
+        if nums[i] != 0:
+            all_zero = False
+            break
+
+    if all_zero:
+        return 0
+
+    diffs: long* = malloc(sizeof(diffs[0]) * len)
+    for i = 1; i < len; i++:
+        diffs[i-1] = nums[i]-nums[i-1]
+
+    result = nums[len-1] + predict_next(diffs, len-1)
+    free(diffs)
+    return result
+
+
+# return value is an array terminated by nums_len=-1
+def main() -> int:
+    f = fopen("sampleinput.txt", "r")
+    assert f != NULL
+
+    line: byte[1000]
+    result: long = 0
+
+    while fgets(line, sizeof(line) as int, f) != NULL:
+        nums: long[100]
+        nnums = 0
+        parts = split_by_ascii_whitespace(line)
+        for p = parts; *p != NULL; p++:
+            assert nnums < sizeof(nums)/sizeof(nums[0])
+            nums[nnums++] = atoll(*p)
+        free(parts)
+
+        result += predict_next(nums, nnums)
+
+    fclose(f)
+
+    printf("%lld\n", result)  # Output: 114
+    return 0

examples/aoc2023/day09/part2.jou

@@ -0,0 +1,62 @@
+import "stdlib/io.jou"
+import "stdlib/ascii.jou"
+import "stdlib/str.jou"
+import "stdlib/mem.jou"
+
+
+def predict_next(nums: long*, len: int) -> long:
+    all_zero = True
+    for i = 0; i < len; i++:
+        if nums[i] != 0:
+            all_zero = False
+            break
+
+    if all_zero:
+        return 0
+
+    diffs: long* = malloc(sizeof(diffs[0]) * len)
+    for i = 1; i < len; i++:
+        diffs[i-1] = nums[i]-nums[i-1]
+
+    result = nums[len-1] + predict_next(diffs, len-1)
+    free(diffs)
+    return result
+
+
+def swap(a: long*, b: long*) -> None:
+    tmp = *a
+    *a = *b
+    *b = tmp
+
+
+def reverse(nums: long*, len: int) -> None:
+    p = nums
+    q = &nums[len-1]
+    while p < q:
+        swap(p++, q--)
+
+
+# return value is an array terminated by nums_len=-1
+def main() -> int:
+    f = fopen("sampleinput.txt", "r")
+    assert f != NULL
+
+    line: byte[1000]
+    result: long = 0
+
+    while fgets(line, sizeof(line) as int, f) != NULL:
+        nums: long[100]
+        nnums = 0
+        parts = split_by_ascii_whitespace(line)
+        for p = parts; *p != NULL; p++:
+            assert nnums < sizeof(nums)/sizeof(nums[0])
+            nums[nnums++] = atoll(*p)
+        free(parts)
+
+        reverse(nums, nnums)
+        result += predict_next(nums, nnums)
+
+    fclose(f)
+
+    printf("%lld\n", result)  # Output: 2
+    return 0

examples/aoc2023/day09/sampleinput.txt

@@ -0,0 +1,3 @@
+0 3 6 9 12 15
+1 3 6 10 15 21
+10 13 16 21 30 45

examples/aoc2023/day10/part1.jou

@@ -0,0 +1,104 @@
+import "stdlib/io.jou"
+import "stdlib/mem.jou"
+import "stdlib/str.jou"
+
+
+class Input:
+    width: int
+    height: int
+    data: byte*
+
+    def is_in_bounds(self, point: int[2]) -> bool:
+        x = point[0]
+        y = point[1]
+        return 0 <= x and x < self->width and 0 <= y and y < self->height
+
+    def get(self, point: int[2]) -> byte:
+        assert self->is_in_bounds(point)
+        x = point[0]
+        y = point[1]
+        return self->data[(self->width + 1)*y + x]
+
+
+def find_S(input: Input*) -> int[2]:
+    for x = 0; x < input->width; x++:
+        for y = 0; y < input->height; y++:
+            if input->get([x, y]) == 'S':
+                return [x, y]
+
+    assert False
+
+
+def get_dirs(c: byte) -> int[2][2]:
+    if c == '7':
+        return [[-1, 0], [0, 1]]
+    if c == 'J':
+        return [[-1, 0], [0, -1]]
+    if c == 'L':
+        return [[1, 0], [0, -1]]
+    if c == 'F':
+        return [[1, 0], [0, 1]]
+    if c == '-':
+        return [[-1, 0], [1, 0]]
+    if c == '|':
+        return [[0, -1], [0, 1]]
+
+    assert False
+
+
+def eq(a: int[2], b: int[2]) -> bool:
+    return a[0] == b[0] and a[1] == b[1]
+
+
+def find_initial_direction(input: Input*, S: int[2]) -> int[2]:
+    directions = [[0,1], [0,-1], [1,0], [-1,0]]
+    for d = &directions[0]; d < &directions[4]; d++:
+        S_to_neighbor = *d
+        neighbor_to_S = [-S_to_neighbor[0], -S_to_neighbor[1]]
+        neighbor = [S[0] + S_to_neighbor[0], S[1] + S_to_neighbor[1]]
+
+        if input->is_in_bounds(neighbor) and input->get(neighbor) != '.':
+            dirs = get_dirs(input->get(neighbor))
+            if eq(dirs[0], S_to_neighbor) or eq(dirs[1], S_to_neighbor):
+                return S_to_neighbor
+
+    assert False
+
+
+def main() -> int:
+    max_len = 100000
+    input = Input{data = calloc(1, max_len+1)}
+
+    f = fopen("sampleinput.txt", "r")
+    assert f != NULL
+    fread(input.data, 1, max_len, f)
+    fclose(f)
+
+    input.width = strcspn(input.data, "\n") as int
+    input.height = (strlen(input.data) as int) / (input.width + 1)
+
+    point = find_S(&input)
+
+    # take first step away from S
+    dir = find_initial_direction(&input, point)
+    point[0] += dir[0]
+    point[1] += dir[1]
+    loop_length = 1
+
+    while input.get(point) != 'S':
+        came_from = [-dir[0], -dir[1]]
+        dirs = get_dirs(input.get(point))
+        assert eq(came_from, dirs[0]) or eq(came_from, dirs[1])
+        if eq(came_from, dirs[0]):
+            dir = dirs[1]
+        else:
+            dir = dirs[0]
+        point[0] += dir[0]
+        point[1] += dir[1]
+        loop_length++
+
+    assert loop_length % 2 == 0
+    printf("%d\n", loop_length / 2)  # Output: 4
+
+    free(input.data)
+    return 0