From 4c42453d856053bb49affef7c165397e5c16d9eb Mon Sep 17 00:00:00 2001
From: Vincent Douillet <vincent@vdouillet.fr>
Date: Sun, 5 Dec 2021 21:28:14 +0100
Subject: day 5

---
 05.c | 118 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 05.c

(limited to '05.c')

diff --git a/05.c b/05.c
new file mode 100644
index 0000000..eeac8ce
--- /dev/null
+++ b/05.c
@@ -0,0 +1,118 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <err.h>
+#include <stdbool.h>
+#include "input.h"
+
+#define INPUT "input/05.txt"
+#define EXPECTED1 6113
+#define EXPECTED2 20373
+
+#define RESOLUTION 1000
+
+#define CMP(a, b) ((a > b) - (a < b))
+
+typedef struct {
+	long p1[2];
+	long p2[2];
+} t_line;
+
+/* sooooo thats about 80KB of memory on my end */
+int space1[RESOLUTION][RESOLUTION];
+int space2[RESOLUTION][RESOLUTION];
+
+void line_list_read(t_line* line_list, struct input_str* input) {
+	for(size_t i = 0; i < input->line_count; i++) {
+		char* start = input->lines[i];
+		char* end = start;
+		line_list[i].p1[0] = strtol(start, &end, 0);
+		start = end + 1; //skip comma
+		line_list[i].p1[1] = strtol(start, &end, 0);
+		start = end + 4; // skip arrow
+		line_list[i].p2[0] = strtol(start, &end, 0);
+		start = end + 1; // skip comma
+		line_list[i].p2[1] = strtol(start, &end, 0);
+	}
+}
+
+void line_print(t_line* line) {
+	printf("%ld,%ld -> %ld,%ld\n", line->p1[0], line->p1[1], line->p2[0], line->p2[1]);
+}
+
+void part1(struct input_str* input) {
+	t_line* line_list = malloc(input->line_count * sizeof(t_line));
+	line_list_read(line_list, input);
+	for(size_t l = 0; l < input->line_count; l++) {
+		t_line line = line_list[l];
+		long x1 = line.p1[0];
+		long y1 = line.p1[1];
+		long x2 = line.p2[0];
+		long y2 = line.p2[1];
+		if(x1 != x2 && y1 != y2) // ignore those for part1
+			continue;
+
+		long dx = -1 * CMP(x1, x2);
+		long dy = -1 * CMP(y1, y2);
+		long x, y;
+		// beware the monster loop
+		for(x = x1, y = y1; (x != x2 + dx || x1 == x2) && (y != y2 + dy || y1 == y2); x += dx, y += dy) {
+			space1[x][y]++;
+		}
+	}
+
+	// count space points with at least a value of 2
+	int result = 0;
+	for(int x = 0; x < RESOLUTION; x++) {
+		for(int y = 0; y < RESOLUTION; y++) {
+			if(space1[x][y] >= 2)
+				result++;
+		}
+	}
+	CHECK(result, EXPECTED1);
+
+	free(line_list);
+}
+
+void part2(struct input_str* input) {
+	t_line* line_list = malloc(input->line_count * sizeof(t_line));
+	line_list_read(line_list, input);
+	for(size_t l = 0; l < input->line_count; l++) {
+		t_line line = line_list[l];
+		long x1 = line.p1[0];
+		long y1 = line.p1[1];
+		long x2 = line.p2[0];
+		long y2 = line.p2[1];
+		long dx = -1 * CMP(x1, x2);
+		long dy = -1 * CMP(y1, y2);
+		long x, y;
+		for(x = x1, y = y1; (x != x2 + dx || x1 == x2) && (y != y2 + dy || y1 == y2); x += dx, y += dy) {
+			space2[x][y]++;
+		}
+	}
+
+	// count space points with at least a value of 2
+	int result = 0;
+	for(int x = 0; x < RESOLUTION; x++) {
+		for(int y = 0; y < RESOLUTION; y++) {
+			if(space2[x][y] >= 2)
+				result++;
+		}
+	}
+	CHECK(result, EXPECTED2);
+
+	free(line_list);
+}
+
+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;
+}
-- 
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