advent-of-code

commit 36ffd870a80acb2cbdb9e1382e52ec0a64576907
parent 7d4f98fdb6170113f67158f9828624d8754097ad
Author: Amin Mesbah <dev@aminmesbah.com>
Date:   Fri,  3 Dec 2021 15:00:21 -0800

Solve 2021 day 2 part 2

Diffstat:
A
2021/day02_02.c
 | 
107
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 107 insertions(+), 0 deletions(-)
diff --git a/2021/day02_02.c b/2021/day02_02.c
@@ -0,0 +1,107 @@
+#if 0
+# Self-building c file. Invoke like: `./file.c`
+outdir=out
+input=$(basename "$0")
+output="$outdir"/$(basename "$0" .c)
+if [ "$input" -nt "$output" ];
+then
+    mkdir --parents "$outdir" || exit
+    echo "Building ${output}." || exit
+    clang -std=c11 -Wall -Wextra -pedantic -Wno-unused-function "$input" -o "$output" || exit
+fi
+if [ "$1" = "-r" ];
+then
+    ./"$output" "$@"
+fi
+exit
+#endif
+
+#include <errno.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+_Noreturn void assert_fail(const char *expr, const char *file, int line, const char *func) {
+    fprintf(stderr, "%s:%d: %s: Assertion failed: '%s'\n", file, line, func, expr);
+    abort();
+}
+
+#define AM_ENABLE_ASSERT 1
+#define AM_ASSERT_FAIL(expr, file, line, func) assert_fail(expr, file, line, func)
+#include "am_base.h"
+#include "am_memory.h"
+#include "am_list.h"
+#include "am_string.h"
+
+Str open_file(MemArena *arena, char *path) {
+    FILE *f = fopen(path, "r");
+    assert(f);
+
+    s32 error = fseek(f, 0L, SEEK_END);
+    assert(!error);
+
+    s64 size = ftell(f);
+    assert(size >= 0);
+    rewind(f);
+
+    u8 *buf = am_mem_arena_push(arena, size);
+    assert(buf);
+
+    size_t items_read = fread(buf, 1, size, f);
+    assert(items_read == (size_t)size);
+
+    error = fclose(f);
+    assert(!error);
+
+    return am_str(buf, size);
+}
+
+int main(void) {
+    MemArena a = am_mem_arena_create(am_mem_base_allocator_malloc());
+    Str input = open_file(&a, "day02_input.txt");
+    StrList tokens = am_str_split(&a, input, (u8 *)"\n ", 2);
+
+    struct {
+        s64 horizontal;
+        s64 depth;
+        s64 aim;
+    } position = {0};
+
+    s64 *dimension = NULL;
+    s64 sign = 0;
+    bool expect_command = true;
+
+    for (StrListNode *token = tokens.first; token; token = token->next) {
+        if (expect_command) {
+            if (am_str_eq(token->s, AM_STR_LIT("forward"))) {
+                dimension = &position.horizontal;
+                sign = 1;
+            } else if (am_str_eq(token->s, AM_STR_LIT("up"))) {
+                dimension = &position.aim;
+                sign = -1;
+            } else if (am_str_eq(token->s, AM_STR_LIT("down"))) {
+                dimension = &position.aim;
+                sign = 1;
+            } else {
+                assert(false);
+            }
+            expect_command = false;
+        } else {
+            assert(dimension);
+            assert(sign == -1 || sign == 1);
+            assert(token->s.size == 1);
+            assert(token->s.str[0] >= '0' && token->s.str[0] <= '9');
+            s64 amount = token->s.str[0] - '0';
+            *dimension += sign * amount;
+            if (dimension == &position.horizontal) {
+                position.depth += position.aim * amount;
+            }
+            expect_command = true;
+        }
+    }
+
+    printf("Multiplied position dimensions: %" PRId64 "\n", position.horizontal * position.depth);
+
+    am_mem_arena_release(&a);
+    return 0;
+}