day 02

day-02/main.c

@@ -0,0 +1,61 @@
+#include "aoc.h"
+
+typedef struct {
+    i32 *data;
+    isize len, cap;
+} Ints;
+
+static bool
+is_safe(i32 *nums, isize len) {
+    bool expect_increase = nums[1] > nums[0];
+    for (isize i = 0; i < len - 1; i++) {
+        i32 a = nums[i], b = nums[i + 1];
+        i32 diff = b - a;
+        if (expect_increase) {
+            if (diff < 0) return false;
+            if (diff > 3) return false;
+            if (diff < 1) return false;
+        }
+        else {
+            if (diff > 0) return false;
+            if (diff < -3) return false;
+            if (diff > -1) return false;
+        }
+    }
+    return true;
+}
+
+static bool
+is_safe_with_exception(i32 *nums, i32 len, Arena temp) {
+    i32 *selection = ARENA_ALLOC_ARRAY(&temp, i32, len - 1);
+    for (isize skip = 0; skip < len; skip++) {
+        memcpy(selection, nums, skip * sizeof(i32));
+        memcpy(selection + skip, nums + skip + 1, (len - skip - 1) * sizeof(i32));
+        if (is_safe(selection, len - 1)) return true;
+    }
+    return false;
+}
+
+int main(int argc, char **argv) {
+    Arena *arena = make_arena(Megabytes(1));
+    Tokens lines = read_lines(arena, argv[1]);
+
+    i32 part_1 = 0;
+    i32 part_2 = 0;
+
+    for (isize i = 0; i < lines.len; i++) {
+        str line = lines.tokens[i];
+        Ints values = {0};
+        Tokens nums = str_tokenize(arena, line, STR(" "));
+        for (isize j = 0; j < nums.len; j++) {
+            *push(&values, arena) = parse_i64(str_trim(nums.tokens[j]), *arena);
+        }
+        part_1 += is_safe(values.data, values.len);
+        part_2 += is_safe_with_exception(values.data, values.len, *arena);
+    }
+    printf("%d\n", part_1);
+    ASSERT(part_1 == 411);
+
+    printf("%d\n", part_2);
+    ASSERT(part_2 == 465);
+}

day-02/test.txt

@@ -0,0 +1,6 @@
+7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9