advent2021

commit 6f73f35dfebaab334028271e8d40c8e0485b7178
parent ec79421a5a9c955ee159e40b0dea1733b8bd1bf5
Author: bsandro <[email protected]>
Date:   Thu,  2 Dec 2021 09:23:55 +0200

Day 02, puzzle 2

Diffstat:
M
day02/main.c
 | 
6
+++---
A
day02/puzzle2.c
 | 
50
++++++++++++++++++++++++++++++++++++++++++++++++++
A
day02/puzzle2.h
 | 
1
+

3 files changed, 54 insertions(+), 3 deletions(-)
diff --git a/day02/main.c b/day02/main.c
@@ -1,6 +1,6 @@
 #include <stdio.h>
 #include "puzzle1.h"
-//#include "puzzle2.h"
+#include "puzzle2.h"
 
 int main(int argc, char *argv[]) {
 	printf("Advent of Code: day 02\n");
@@ -17,8 +17,8 @@ int main(int argc, char *argv[]) {
 
 	int counter1 = puzzle1(filename);
 	printf("Puzzle #1: %d\n", counter1);
-	//int counter2 = puzzle2(filename);
-	//printf("Puzzle #2: %d\n", counter2);
+	int counter2 = puzzle2(filename);
+	printf("Puzzle #2: %d\n", counter2);
 
 	return 0;
 }
diff --git a/day02/puzzle2.c b/day02/puzzle2.c
@@ -0,0 +1,50 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <strings.h>
+
+#define MAX_LEN 32
+#define MAX_CMD 16
+
+int puzzle2(const char *filename) {
+	FILE *infile = fopen(filename, "r");
+	if (infile == NULL) {
+		fprintf(stderr, "fopen() error: %s\n", strerror(errno));
+		return -1;
+	}
+
+	static const char *cmd_up = "up";
+	static const char *cmd_down = "down";
+	static const char *cmd_forward = "forward";
+	char buf[MAX_LEN] = {0};
+	char cmd[MAX_CMD] = {0};
+	int depth = 0;
+	int distance = 0;
+	int aim = 0;
+	int arg = 0;
+
+	while (fgets(buf, MAX_LEN, infile) != NULL) {
+		if (sscanf(buf, "%15s %d", cmd, &arg) == 2) {
+			if (strncmp(cmd, cmd_up, MAX_CMD) == 0) {
+				aim -= arg;
+			} else if (strncmp(cmd, cmd_down, MAX_CMD) == 0) {
+				aim += arg;
+			} else if (strncmp(cmd, cmd_forward, MAX_CMD) == 0) {
+				distance += arg;
+				depth += aim * arg;
+			} else {
+				fprintf(stderr, "Invalid command string");
+				break;
+			}
+
+			bzero(buf, MAX_LEN);
+			bzero(cmd, MAX_CMD);
+		}
+	}
+
+	// mutiny! ignoring feof/ferror.
+
+	fclose(infile);
+	return depth * distance;
+}
diff --git a/day02/puzzle2.h b/day02/puzzle2.h
@@ -0,0 +1 @@
+int puzzle2(const char *filename);