aoc-2019-c

commit 3ef16bed60d82e4d87ba93d90c891615d4078d87
parent a9998acb73c9d2a482d00643687fd3aae187c57c
Author: Louis Burda <quent.burda@gmail.com>
Date:   Tue,  2 Nov 2021 18:01:48 +0100

Add day 4

Diffstat:
M
src/day4/main.c
 | 
94
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
A
src/day4/part2
 | 
22
++++++++++++++++++++++
A
src/day4/test.input
 | 
1
+

3 files changed, 115 insertions(+), 2 deletions(-)
diff --git a/src/day4/main.c b/src/day4/main.c
@@ -3,14 +3,104 @@
 #include <stdlib.h>
 #include <stdio.h>
 
+int
+check_pass_1(int *state)
+{
+	int i;
+
+	for (i = 0; i < 5; i++)
+		if (state[i] == state[i+1])
+			break;
+
+	if (i != 5) debug("%i %i %i %i %i %i\n", state[0], state[1],
+		state[2], state[3], state[4], state[5]);
+
+	return i != 5;
+}
+
+int
+check_pass_2(int *state)
+{
+	int i;
+
+	for (i = 0; i < 5; i++) {
+		if (state[i] == state[i+1] && (i == 0 || state[i] != state[i-1])
+				&& (i == 4 || state[i] != state[i+2]))
+			break;
+	}
+
+	if (i != 5) debug("%i %i %i %i %i %i\n", state[0], state[1],
+		state[2], state[3], state[4], state[5]);
+
+	return i != 5;
+}
+
 void
-part1()
+count_valid(int *state, int *end, int pinit, int pend,
+	int index, int *count, int (*check_pass)(int*))
 {
+	int i;
+
+	if (index == 6) {
+		*count += check_pass(state);
+		return;
+	}
+
+	if (index && pinit && state[index-1] > state[index]) {
+		pinit = 0;
+		state[index] = state[index-1];
+	} else if (index && !pinit) {
+		state[index] = state[index-1];
+	}
+
+	for (i = state[index]; i <= (pend ? end[index] : 9); i++) {
+		state[index] = i;
+		count_valid(state, end, pinit, pend && (i == end[index]),
+			index+1, count, check_pass);
+	}
 
+	state[index] = 0;
 }
 
 void
-part2()
+read_state(char *str, int *state)
 {
+	int i;
+
+	for (i = 0; i < 6; i++)
+		state[i] = str[i] - '0';
+}
+
+void
+part1(void)
+{
+	int start[6], end[6];
+	char *tok;
+	int count;
+
+	tok = CHKP(strchr(aoc.input, '-'));
+	read_state(aoc.input, start);
+	read_state(tok+1, end);
+
+	count = 0;
+	count_valid(start, end, 1, 1, 0, &count, check_pass_1);
+
+	aoc.answer = aprintf("%i", count);
+}
+
+void
+part2(void)
+{
+	int start[6], end[6];
+	char *tok;
+	int count;
+
+	tok = CHKP(strchr(aoc.input, '-'));
+	read_state(aoc.input, start);
+	read_state(tok+1, end);
+
+	count = 0;
+	count_valid(start, end, 1, 1, 0, &count, check_pass_2);
 
+	aoc.answer = aprintf("%i", count);
 }
diff --git a/src/day4/part2 b/src/day4/part2
@@ -0,0 +1,22 @@
+--- Part Two ---
+
+An Elf just remembered one more important detail: the two adjacent matching digits are not
+part of a larger group of matching digits.
+
+Given this additional criterion, but still ignoring the range rule, the following are now true:
+
+
+ - 112233 meets these criteria because the digits never decrease and all repeated digits are exactly
+two digits long.
+
+ - 123444 no longer meets the criteria (the repeated 44 is part of a larger group of
+444).
+
+ - 111122 meets the criteria (even though 1 is repeated more than twice, it still contains a double
+22).
+
+
+How many different passwords within the range given in your puzzle input meet all of
+the criteria?
+
+
diff --git a/src/day4/test.input b/src/day4/test.input
@@ -0,0 +1 @@
+111002-111122