day 2 part 1

day_2/1.c

@@ -0,0 +1,72 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+
+typedef struct levels {
+  size_t mem_size;
+  size_t size;
+  unsigned int *data;
+} levels_t;
+
+int main(void) {
+  FILE *fp = fopen("input", "r");
+
+  if (fp == NULL) {
+    perror("input");
+    return 1;
+  }
+
+  char *line = NULL;
+  size_t size;
+
+  levels_t levels;
+  levels.mem_size = 10;
+  levels.size = 0;
+  levels.data = malloc(sizeof(unsigned int) * levels.mem_size);
+
+  unsigned int sum = 0;
+  while (getline(&line, &size, fp) > 0) {
+    char *next = strtok(line, " ");
+
+    while (next != NULL) {
+      if (levels.size >= levels.mem_size) {
+        levels.mem_size *= 2;
+        levels.data =
+            realloc(levels.data, levels.mem_size * sizeof(unsigned int));
+      }
+
+      sscanf(next, "%u", &levels.data[levels.size]);
+      levels.size++;
+
+      next = strtok(NULL, " ");
+    }
+
+    bool safe = true;
+    int diff = levels.data[1] - levels.data[0];
+    int increasing = diff > 0 ? 1 : -1;
+    for (int i = 1; i < levels.size; i++) {
+      diff = increasing * (levels.data[i] - levels.data[i - 1]);
+
+      if (diff < 1 || diff > 3) {
+        safe = false;
+        break;
+      }
+    }
+
+    if (safe) {
+      sum++;
+    }
+
+    levels.size = 0;
+  }
+
+  free(line);
+  free(levels.data);
+
+  printf("%u\n", sum);
+
+  fclose(fp);
+
+  return 0;
+}