advent-of-code

commit 70701b9b997344026cbbbc5ff2c14c1a513aa3d1
parent a11c5cfa69db7d5291269e66a4aa64bf67cb6212
Author: amin <dev@aminmesbah.com>
Date:   Fri,  3 Dec 2021 22:33:57 +0000

Solve 2021 day 1 part 2

FossilOrigin-Name: 0f7131eeacfd5b3ed0ca746896d41f85b7a2dde9eb0e291d0d1a5c502317d2a6
Diffstat:
A
2021/day01_02.c
 | 
91
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 91 insertions(+), 0 deletions(-)
diff --git a/2021/day01_02.c b/2021/day01_02.c
@@ -0,0 +1,91 @@
+#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 <inttypes.h>
+#include <errno.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, "day01_input.txt");
+    StrList lines = am_str_split(&a, input, (u8 *)"\n", 1);
+    assert(lines.node_count >= 3);
+
+    u64 increase_count = 0;
+    u64 previous_sum = UINT64_MAX;
+    u64 window[3] = {0};
+    u64 window_i = 0;
+    u64 line_number = 0;
+
+    for (StrListNode *line = lines.first; line; line = line->next) {
+        u64 number = 0;
+        for (usz i = 0; i < line->s.size; i++) {
+            u64 digit = line->s.str[i] - '0';
+            number = (number * 10) + digit;
+        }
+
+        window[window_i] = number;
+        window_i = (window_i + 1) % 3;
+
+        line_number++;
+        if (line_number >= 3) {
+            u64 sum = window[0] + window[1] + window[2];
+            increase_count += (sum > previous_sum);
+            previous_sum = sum;
+        }
+    }
+
+    printf("Increase Count: %" PRIu64 "\n", increase_count);
+    am_mem_arena_release(&a);
+    return 0;
+}