From 3e0f83d638a38902621edfdbbabcafdeb2a8aa38 Mon Sep 17 00:00:00 2001
From: Mart Lubbers <mart@martlubbers.net>
Date: Fri, 11 Dec 2020 14:23:56 +0100
Subject: [PATCH] c implementatino

---
 11/one.c | 113 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)
 create mode 100644 11/one.c

diff --git a/11/one.c b/11/one.c
new file mode 100644
index 0000000..c6fb07e
--- /dev/null
+++ b/11/one.c
@@ -0,0 +1,113 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+enum cellstatus {floor, empty, occup, oob};
+
+uint16_t map1[100][100] = {oob};
+uint16_t map2[100][100] = {oob};
+int xmax, ymax;
+
+enum cellstatus seat(int x, int y, uint16_t map[100][100])
+{
+	return x < 0 || y < 0 || x >= xmax || y >= ymax ? oob
+		: (enum cellstatus)((map[x][y] >> 8) & 0xff);
+}
+
+bool lookone(int x, int y, int dx, int dy, uint16_t map[100][100])
+{
+	return seat(x+dx, y+dy, map) == occup;
+}
+
+bool looktwo(int x, int y, int dx, int dy, uint16_t map[100][100])
+{
+	enum cellstatus s;
+	while((s = seat(x += dx, y += dy, map)) == floor);
+	return s == occup;
+}
+
+bool step(bool (*lookfun)(int, int, int, int, uint16_t map[100][100]), int die, uint16_t map[100][100])
+{
+	//Move the old to the leftmost byte
+	for (int y = 0; y<ymax; y++)
+		for (int x = 0; x<xmax; x++)
+			map[x][y] <<= 8;
+	//Do a step
+	bool same = true;
+	for (int y = 0; y<ymax; y++) {
+		for (int x = 0; x<xmax; x++) {
+			enum cellstatus st = seat(x, y, map);
+			if (st == floor) {
+				map[x][y] |= floor;
+				continue;
+			}
+			int count = 0;
+			for (int dx = -1; dx<=1; dx++) {
+				for (int dy = -1; dy<=1; dy++) {
+					if (dx == 0 && dy == 0)
+						continue;
+					if (lookfun(x, y, dx, dy, map))
+						count++;
+				}
+			}
+			if (st == empty) {
+				if (count == 0) {
+					same = false;
+					map[x][y] |= occup;
+				} else {
+					map[x][y] |= empty;
+				}
+			} else if(st == occup) {
+				if (count >= die) {
+					same = false;
+					map[x][y] |= empty;
+				} else {
+					map[x][y] |= occup;
+				}
+			}
+		}
+	}
+	return same;
+}
+
+int main()
+{
+	int x = 0, y = 0;
+	int c;
+	while ((c = getchar()) != EOF) {
+		switch (c) {
+		case 'L':
+			map1[x][y] = empty;
+			map2[x++][y] = empty;
+			break;
+		case '.':
+			map1[x][y] = floor;
+			map2[x++][y] = floor;
+			break;
+		case '\n':
+			xmax = x;
+			x = 0;
+			y++;
+			break;
+		}
+	}
+	ymax = y;
+
+	//Do one
+	while(!step(lookone, 4, map1));
+
+	//Do two
+	while(!step(looktwo, 5, map2));
+
+	int count1 = 0, count2 = 0;
+	for (int y = 0; y<ymax; y++) {
+		for (int x = 0; x<xmax; x++) {
+			if ((map1[x][y] & 0xff) == occup)
+				count1++;
+			if ((map2[x][y] & 0xff) == occup)
+				count2++;
+		}
+	}
+	printf("one: %d, two: %d\n", count1, count2);
+	return 0;
+}
-- 
2.20.1