Added: day 1 part 1

day1/day1.c

@@ -0,0 +1,61 @@
+/*
+	Dial from 0–99, start at 50.
+	You get lines like L68 or R5:
+	L = move left (subtract)
+	R = move right (add)
+	Wrap around with modulo 100.
+	After each move, check if the dial is on 0.
+	The password = how many times you land on 0 during the whole sequence.
+*/
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char* argv[]) {
+	printf("Advent Of Code Day 1\n\n");
+
+	// remove argc so gcc wont cry
+	(void)argc;
+
+	// base vars
+	int start = 50;
+	int pos = start;
+	int counter = 0;
+
+	// read the input file
+	char* inpf = NULL;
+	inpf = argv[1];
+	if (inpf == NULL) inpf = "input.txt";
+
+	FILE* ptr = fopen(inpf, "r");
+	if(ptr == NULL) {
+		printf("error: no such file %s\n", inpf);
+		return 1;
+	}
+	
+
+	// process instructions
+	char line[9]; // 8 chars + eol
+	while(fscanf(ptr, "%4s", line) == 1) {
+		//printf("current position: %d\n", pos);
+		char drc = line[0];
+		int num = atoi(&line[1]);
+		//printf("%c %d\n", drc, num);
+
+		if (drc == 'R') pos += num;
+		if (drc == 'L') pos -= num;
+
+		while (pos > 99) {
+			pos -= 100;
+		}
+
+		while (pos < 0){ 
+			pos += 100;
+		}
+
+		if (pos == 0) counter++;
+	}
+
+	//printf("current position: %d\n", pos);
+	printf("\npassword is: %d\n", counter);
+	return 0;
+}