Add 2025 day 3 solutions

3 files changed, 50 insertions, 0 deletions

diff --git a/2025/03/.gitignore b/2025/03/.gitignore
new file mode 100644
index 0000000..60d075d
--- /dev/null
+++ b/2025/03/.gitignore
@@ -0,0 +1 @@
+puzzle-[12]
diff --git a/2025/03/Makefile b/2025/03/Makefile
new file mode 100644
index 0000000..de3f940
--- /dev/null
+++ b/2025/03/Makefile
@@ -0,0 +1 @@
+include ../../Makefiles/c.mk
diff --git a/2025/03/puzzles.c b/2025/03/puzzles.c
new file mode 100644
index 0000000..9bd68ee
--- /dev/null
+++ b/2025/03/puzzles.c
@@ -0,0 +1,48 @@
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef PART1
+	#define DIGITS ((size_t)(2))
+#else
+	#define DIGITS ((size_t)(12))
+#endif
+
+int
+main(void)
+{
+	FILE *fp = fopen("input", "r");
+	if (fp == nullptr)
+		err(EXIT_FAILURE, "failed to open input");
+
+	char *buf = nullptr;
+	size_t acc, bufsz;
+	ssize_t n;
+
+	acc = bufsz = 0;
+
+	while ((n = getline(&buf, &bufsz, fp)) != -1) {
+		if (buf[n - 1] == '\n')
+			buf[--n] = 0;
+
+		char digits[DIGITS + 1];
+		memcpy(digits, buf, DIGITS);
+		digits[DIGITS] = 0;
+
+		for (size_t i = 1; i < n - DIGITS + 1; i++) {
+			for (size_t j = 0; j < DIGITS; j++) {
+				if (buf[i + j] > digits[j])
+					memcpy(digits + j, buf + i + j, DIGITS - j);
+			}
+		}
+
+		acc += (size_t)strtol(digits, nullptr, 10);
+	}
+	if (ferror(fp))
+		err(EXIT_FAILURE, "failed to read record");
+
+	fclose(fp);
+	printf("%zu\n", acc);
+	return EXIT_SUCCESS;
+}