Initial commit

2020/day05/day05.c

@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <limits.h>
+#include <stdbool.h>
+
+unsigned int bin_to_int(char *buf, int size) {
+  unsigned int r = 0;
+  for (int i = 0; i < size; ++i) {
+    r = r << 1;
+    if (buf[i] == 'B' || buf[i] == 'R') {
+      r++;
+    }
+  }
+  return r;
+}
+
+int main(int argc, char *argv[])
+{
+  if (argc < 2) {
+    printf("Usage: %s <input file>\n", argv[0]);
+    return 0;
+  }
+
+  FILE *fp = fopen(argv[1], "r");
+  if (fp == NULL) {
+    printf("Could not open file %s\n", argv[1]);
+    return 1;
+  }
+
+  char buf[12];
+  size_t i = 0;
+  unsigned int ids[1024];
+  unsigned int min_id = UINT_MAX;
+  unsigned int max_id = 0;
+  while (fgets(buf, sizeof(buf), fp) != NULL) {
+    ids[i] = bin_to_int(buf, 10);
+    if (min_id > ids[i]) {
+      min_id = ids[i];
+    }
+    if (max_id < ids[i]) {
+      max_id = ids[i];
+    }
+    i++;
+  }
+  printf("%u\n", max_id);
+
+  fclose(fp);
+
+  for (int id = min_id; id < max_id; ++id) {
+    bool present = false;
+    for (int j = 0; j < i; ++j) {
+      present = present || (id == ids[j]);
+    }
+    if (!present) {
+      printf("%u\n", id);
+      break;
+    }
+  }
+
+  return 0;
+}