Advent of code 2022 problems 1-4

1 files changed, 53 insertions, 0 deletions

diff --git a/4a.c b/4a.c
new file mode 100644
index 0000000..76d5e0c
--- /dev/null
+++ b/4a.c
@@ -0,0 +1,53 @@
+
+#include <stdio.h>
+#include <stdlib.h>
+
+
+char *
+getsect(int * dest, char * pch, char expect)
+{
+	char * end;
+
+	if (!pch)
+		return NULL;
+	*dest = strtol(pch, &end, 10);
+	if (*dest == 0 && end == pch)
+		return NULL;
+	if (*end != expect)
+		return NULL;
+	if (expect)
+		++end;
+	return end;
+}
+
+
+int
+main()
+{
+	char buf[BUFSIZ];
+	int overlaps = 0;
+
+	while (fgets(buf, sizeof(buf), stdin)) {
+		int n[4];
+		char * pbuf;
+
+		pbuf = getsect(&n[0], buf, '-');
+		pbuf = getsect(&n[1], pbuf, ',');
+		pbuf = getsect(&n[2], pbuf, '-');
+		pbuf = getsect(&n[3], pbuf, '\n');
+		if (!pbuf) {
+			fprintf(stderr, "Unexpected line: %s\n", buf);
+			return -1;
+		}
+		if ((n[2] >= n[0] && n[3] <= n[1])
+				|| (n[0] >= n[2] && n[1] <= n[3]))
+		{
+			++overlaps;
+		}
+	}
+
+	printf("Overlaps: %d\n", overlaps);
+
+	return 0;
+}
+