From 40aa90ca888cbe67552893ba82f83b8f80b0c43f Mon Sep 17 00:00:00 2001
From: Vincent Douillet <vincent@vdouillet.fr>
Date: Wed, 8 Dec 2021 09:51:04 +0100
Subject: day 7

---
 07.c     | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 Makefile |  5 +++-
 2 files changed, 99 insertions(+), 1 deletion(-)
 create mode 100644 07.c

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;
+}
diff --git a/Makefile b/Makefile
index 97c64b6..a2e394d 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 CC=cc
 CFLAGS=-std=c1x -W -Wall -g
 LDFLAGS=
-EXEC=01 02 03 04 05 06
+EXEC=01 02 03 04 05 06 07
 
 all: $(EXEC)
 
@@ -26,5 +26,8 @@ all: $(EXEC)
 06: input.o list.o 06.o
 	$(CC) -o $@ $> $(LDFLAGS)
 
+07: input.o 07.o
+	$(CC) -o $@ $> $(LDFLAGS)
+
 clean:
 	rm -rf *.o $(EXEC)
-- 
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