AOC2023: implement day1

userspace/aoc2023/day1/main.cpp

@@ -1,6 +1,129 @@
+#include <ctype.h>
 #include <stdio.h>
+#include <string.h>
 
-int main()
+int puzzle1(FILE* fp)
 {
-	printf("hello world\n");
+	int sum = 0;
+
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		int line_len = strlen(buffer);
+
+		for (int i = 0; i < line_len; i++)
+		{
+			if (!isdigit(buffer[i]))
+				continue;
+			sum += 10 * (buffer[i] - '0');
+			break;
+		}
+
+		for (int i = line_len - 1; i >= 0; i--)
+		{
+			if (!isdigit(buffer[i]))
+				continue;
+			sum += buffer[i] - '0';
+			break;
+		}
+	}
+
+	return sum;
+}
+
+int puzzle2(FILE* fp)
+{
+	const char* str_digits[] = {
+		"zero",
+		"one",
+		"two",
+		"three",
+		"four",
+		"five",
+		"six",
+		"seven",
+		"eight",
+		"nine"
+	};
+
+	int sum = 0;
+
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		int line_len = strlen(buffer);
+
+		int digit = -1;
+
+		for (int i = 0; i < line_len; i++)
+		{
+			if (isdigit(buffer[i]))
+			{
+				digit = buffer[i] - '0';
+				break;
+			}
+			for (int j = 0; j < 10; j++)
+			{
+				if (line_len - i < strlen(str_digits[j]))
+					continue;
+				if (strncmp(buffer + i, str_digits[j], strlen(str_digits[j])) == 0)
+				{
+					digit = j;
+					break;
+				}
+			}
+			if (digit != -1)
+				break;
+		}
+		sum += 10 * digit;
+
+		digit = -1;
+
+		for (int i = line_len - 1; i >= 0; i--)
+		{
+			if (isdigit(buffer[i]))
+			{
+				digit = buffer[i] - '0';
+				break;
+			}
+			for (int j = 0; j < 10; j++)
+			{
+				if (i < strlen(str_digits[j]))
+					continue;
+				if (strncmp(buffer + i - strlen(str_digits[j]), str_digits[j], strlen(str_digits[j])) == 0)
+				{
+					digit = j;
+					break;
+				}
+			}
+			if (digit != -1)
+				break;
+		}
+
+		sum += digit;
+	}
+
+	return sum;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2023/day1_input.txt";
+	if (argc >= 2)
+		file_path = argv[1];
+
+	FILE* fp = fopen(file_path, "r");
+	if (fp == nullptr)
+	{
+		perror("fopen");
+		return 1;
+	}
+
+	printf("puzzle1: %d\n", puzzle1(fp));
+
+	fseek(fp, 0, SEEK_SET);
+
+	printf("puzzle2: %d\n", puzzle2(fp));
+
+	fclose(fp);
 }