day 7

1 files changed, 95 insertions, 0 deletions

diff --git a/07.c b/07.c
new file mode 100644
index 0000000..20caf95
--- /dev/null
+++ b/07.c
@@ -0,0 +1,95 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <limits.h>
+#include "input.h"
+
+#define ABS(x) (x < 0 ? -(x) : x)
+#define MIN(x, y) (x < y ? x : y)
+
+#define INPUT "input/07.txt"
+#define INPUT_DOMAIN_MAX 2000
+
+#define EXPECTED1 349769L
+#define EXPECTED2 99540554L
+
+void part1(struct input_str* input) {
+	char* start = input->lines[0];
+	char* end = start;
+	int sub_count_by_alt[INPUT_DOMAIN_MAX] = { 0 };
+
+	// parse input
+	long sub_count = 0;
+	while(*end != '\n') {
+		long alt = strtol(start, &end, 0);
+		start = end;
+		if(*end == ',')
+			start++;
+
+		sub_count_by_alt[alt]++;
+		sub_count++;
+	}
+
+	// brute force
+	long fuel_min = LONG_MAX;
+	for(int a = 0; a < INPUT_DOMAIN_MAX; a++) {
+		long current_fuel = 0;
+		for(int b = 0; b < INPUT_DOMAIN_MAX; b++) {
+			current_fuel += sub_count_by_alt[b] * ABS(b - a);
+		}
+		fuel_min = MIN(fuel_min, current_fuel);
+	}
+	
+	CHECK(fuel_min, EXPECTED1);
+}
+
+long compute_fuel(int distance) {
+	long fuel = 0;
+	for(int i = 1; i <= distance; i++) {
+		fuel += i;
+	}
+	return fuel;
+}
+
+void part2(struct input_str* input) {
+	char* start = input->lines[0];
+	char* end = start;
+	int sub_count_by_alt[INPUT_DOMAIN_MAX] = { 0 };
+
+	// parse input
+	long sub_count = 0;
+	while(*end != '\n') {
+		long alt = strtol(start, &end, 0);
+		start = end;
+		if(*end == ',')
+			start++;
+
+		sub_count_by_alt[alt]++;
+		sub_count++;
+	}
+
+	// brute force
+	long fuel_min = LONG_MAX;
+	for(int a = 0; a < INPUT_DOMAIN_MAX; a++) {
+		long current_fuel = 0;
+		for(int b = 0; b < INPUT_DOMAIN_MAX; b++) {
+			current_fuel += sub_count_by_alt[b] * compute_fuel(ABS(b - a));
+		}
+		fuel_min = MIN(fuel_min, current_fuel);
+	}
+	
+	CHECK(fuel_min, EXPECTED2);
+}
+
+int main() {
+	// read input
+	struct input_str input;
+	input_str_read(&input, INPUT);
+
+	// do stuff
+	part1(&input);
+	part2(&input);
+
+	// cleanup & exit
+	input_str_free(&input);
+	return 0;
+}