Advent of code 2022 problems 1-4

1 files changed, 65 insertions, 0 deletions

diff --git a/3a.c b/3a.c
new file mode 100644
index 0000000..676db86
--- /dev/null
+++ b/3a.c
@@ -0,0 +1,65 @@
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+
+int
+chrcmp(void const * a, void const * b)
+{
+	return (*(char const *) a) - *((char const *) b);
+}
+
+
+int
+priority(int c)
+{
+	if (c >= 'A' && c <= 'Z')
+		return 27 + c - 'A';
+	if (c >= 'a' && c <= 'z')
+		return 1 + c - 'a';
+	fprintf(stderr, "Unexpected priority request: %c\n", c);
+	return -1;
+}
+
+
+int
+main()
+{
+	char buf[BUFSIZ];
+	int score = 0;
+
+	while (fgets(buf, sizeof(buf), stdin)) {
+		int len, i, j;
+
+		len = strlen(buf);
+		if (len && buf[len - 1] == '\n')
+			--len;
+		if (len % 2 == 1)
+			fprintf(stderr, "Unexpected length: %d\n", len);
+
+		qsort(buf, len / 2, 1, chrcmp);
+		qsort(buf + len / 2, len / 2, 1, chrcmp);
+
+		i = 0;
+		j = len / 2;
+		while (i < len / 2 && j < len) {
+			if (buf[i] < buf[j])
+				++i;
+			else if (buf[j] < buf[i])
+				++j;
+			else
+				break;
+		}
+		if (i >= len / 2 || j >= len) {
+			fprintf(stderr, "No match found in %s\n", buf);
+			return -1;
+		}
+		score += priority(buf[i]);
+	}
+
+	printf("Score: %d\n", score);
+
+	return 0;
+}
+