day 1: trebuchetHEADmain

1 files changed, 117 insertions, 0 deletions

diff --git a/trebuchet/trebuchet.c b/trebuchet/trebuchet.c
new file mode 100644
index 0000000..72e735e
--- /dev/null
+++ b/trebuchet/trebuchet.c
@@ -0,0 +1,117 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+static int first_half(FILE *fp) {
+	size_t total = 0, size;
+	ssize_t len;
+	ssize_t first, last;
+	char *line = NULL;
+	while ((len = getline(&line, &size, fp)) != -1) {
+		line[--len] = '\0';
+		first = last = -1;
+		for (size_t i = 0; i <= len; i++) {
+			if (first == -1 && isdigit(line[i])) {
+				first = line[i] - '0';
+			}
+
+			if (last == -1 && isdigit(line[len - i])) {
+				last = line[len - i] - '0';
+			}
+
+			if (first > -1 && last > -1)
+				break;
+		}
+
+		if (first == -1 || last == -1) {
+			fprintf(stderr, "failed to find digit in input string: %s\n", line);
+			free(line);
+			return EXIT_FAILURE;
+		}
+		total += (first * 10) + last;
+	}
+
+	free(line);
+	printf("result: %ld\n", total);
+	return EXIT_SUCCESS;
+}
+
+const struct {
+	size_t num;
+	char *text;
+} table[] = {
+	{ 1, "one" },
+	{ 2, "two" },
+	{ 3, "three" },
+	{ 4, "four" },
+	{ 5, "five" },
+	{ 6, "six" },
+	{ 7, "seven" },
+	{ 8, "eight" },
+	{ 9, "nine" },
+};
+
+inline static ssize_t lookup_num(char *line, size_t i) {
+	if (isdigit(line[i]))
+		return line[i] - '0';
+
+	for (size_t t = 0; t < sizeof(table) / sizeof(*table); t++)
+		if (strncmp(&line[i], table[t].text, strlen(table[t].text)) == 0)
+			return table[t].num;
+
+	return -1;
+}
+
+static int second_half(FILE *fp) {
+	size_t total = 0, size;
+	ssize_t len;
+	ssize_t first, last;
+	char *line = NULL;
+	while ((len = getline(&line, &size, fp)) != -1) {
+		line[--len] = '\0';
+		first = last = -1;
+		for (size_t i = 0; i <= len; i++) {
+			if (first == -1)
+				first = lookup_num(line, i);
+			if (last == -1)
+				last = lookup_num(line, len - i);
+
+			if (first > -1 && last > -1)
+				break;
+		}
+
+		if (first == -1 || last == -1) {
+			fprintf(stderr, "failed to find digit in input string: %s\n", line);
+			free(line);
+			return EXIT_FAILURE;
+		}
+		total += (first * 10) + last;
+	}
+
+	free(line);
+	printf("result: %ld\n", total);
+	return EXIT_SUCCESS;
+}
+
+int main(int argc, char **argv) {
+	if (argc != 2) {
+		fprintf(stderr, "usage: %s <input>\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	FILE *fp = fopen(argv[1], "r");
+	if (!fp) {
+		fprintf(stderr, "failed to open input file: %s\n", argv[1]);
+		return EXIT_FAILURE;
+	}
+
+	const char *half;
+	int ret;
+	if ((half = getenv("AOC_TREBUCHET_HALF")) && strcmp(half, "first") == 0)
+		ret = first_half(fp);
+	else
+		ret = second_half(fp);
+	fclose(fp);
+	return ret;
+}