Initial commit

2020/day02/day02.c

@@ -0,0 +1,45 @@
+#include <stdbool.h>
+#include <stdio.h>
+
+bool is_valid_part1(int lower, int upper, char key, char *pass) {
+  int count = 0;
+  for (char *c = pass; *c != 0; ++c) {
+    if (*c == key) {
+      count++;
+    }
+  }
+  return (count >= lower) && (count <= upper);
+}
+
+bool is_valid_part2(int pos1, int pos2, char key, char *pass) {
+  return (pass[pos1 - 1] == key) ^ (pass[pos2 - 1] == key);
+}
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    printf("Usage: %s <input file>\n", argv[0]);
+    return 0;
+  }
+  FILE *input = fopen(argv[1], "r");
+
+  int lower, upper;
+  char key;
+  char pass[256];
+
+  int count1 = 0;
+  int count2 = 0;
+
+  while (fscanf(input, "%d-%d %c: %s", &lower, &upper, &key, pass) == 4) {
+    if (is_valid_part1(lower, upper, key, pass)) {
+      count1++;
+    }
+    if (is_valid_part2(lower, upper, key, pass)) {
+      count2++;
+    }
+  }
+
+  printf("Part 1: %d\n", count1);
+  printf("Part 2: %d\n", count2);
+
+  return 0;
+}