Day2

day2/c/day2.c

@@ -0,0 +1,80 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define CHARS_MAX 64
+#define MAX_LEVELS 16
+#define abs(a) ((a) < 0 ? (-(a)) : (a))
+
+int is_safe(int *levels, int level_count);
+
+int main() {
+    char *p, *buf, c;
+
+    buf = calloc(CHARS_MAX, sizeof(char));
+    p = buf;
+    int safes1 = 0, safes2 = 0;
+
+    int levels[MAX_LEVELS], level_count = 0;
+    while ((c = getchar()) != EOF) {
+        *p++ = c;
+        if (c != '\n') {
+            continue;
+        }
+        p = buf;
+        int level = 0;
+
+        p--;
+        do {
+            p++;
+            sscanf(p, "%i", &levels[level_count]);
+            level_count++;
+            while (*p != ' ' && *p != '\n') p++;
+        } while(*p != '\n');
+
+        if (is_safe(levels, level_count)) {
+            safes1++;
+        }
+
+        int new_levels[MAX_LEVELS];
+        for (int i = 0; i < level_count; i++) {
+            memcpy(new_levels, levels, level_count * sizeof(levels[0]));
+            for (int j = i; j < level_count - 1; j++) {
+                new_levels[j] = levels[j+1];
+            }
+
+            if (is_safe(new_levels, level_count - 1)) {
+                safes2++;
+                break;
+            }
+        }
+
+        memset(buf, 0, CHARS_MAX);
+        p = buf;
+        level_count = 0;
+    }
+
+    free(buf);
+
+    printf("%i\n", safes1);
+    printf("%i\n", safes2);
+}
+
+int is_safe(int *levels, int level_count) {
+    int diff = 0, safe = 1;
+    for (int i = 0; i < level_count; i++) {
+        if (i != 0) {
+            if (abs(levels[i] - levels[i-1]) < 1 || abs(levels[i] - levels[i-1]) > 3) {
+                safe = 0;
+            }
+
+            if ((levels[i] - levels[i-1]) * diff < 0) {
+                safe = 0;
+            }
+
+            diff = levels[i] - levels[i-1];
+        }
+    }
+
+    return safe;
+}