5 files changed, 1022 insertions, 0 deletions
diff --git a/2021/day13/day13 b/2021/day13/day13
new file mode 100755
index 0000000..0d614ac
--- /dev/null
+++ b/2021/day13/day13
diff --git a/2021/day13/day13.cpp b/2021/day13/day13.cpp
new file mode 100644
index 0000000..65f852f
--- /dev/null
+++ b/2021/day13/day13.cpp
@@ -0,0 +1,99 @@
+#include <iostream>
+#include <fstream>
+#include <vector>
+#include <string>
+#include "../utils.h"
+
+class Fold {
+	public: Fold(bool axis, int i) : axis(axis), i(i) { }
+	int i; bool axis;
+};
+
+class Dot {
+	public: Dot(int x, int y) : x(x), y(y) { }
+	int x, y;
+};
+
+
+void show (std::vector<Dot> dots, bool vis) {
+	int minx = 99999, maxx = -99999;
+	int miny = 99999, maxy = -99999;
+	for (Dot dot : dots) {
+		minx = std::min(minx, dot.x);
+		miny = std::min(miny, dot.y);
+		maxx = std::max(maxx, dot.x);
+		maxy = std::max(maxy, dot.y);
+	}
+	int count = 0;
+	int sizex = maxx-minx+1;
+	int sizey = maxy-miny+1;
+	for (int y=0; y<sizey; y++) {
+		for (int x=0; x<sizex; x++) {
+			bool occ = false;
+			for (Dot dot : dots) {
+				if (dot.x == x && dot.y == y) {
+					occ = true; break;
+				}
+			}
+			if (occ) {
+				count ++;
+				if (vis) std::cout << "#";
+			}
+			else if (vis) std::cout << ".";
+		}
+		if (vis) std::cout << std::endl;
+	}
+
+	std::cout << "dots remaining: " << count << std::endl;
+}
+
+void fold (std::vector<Dot> &dots, Fold f) {
+	for (Dot &dot : dots) {
+		if (f.axis) { 
+			int dist = f.i - dot.x;
+			if (dist < 0) dot.x = f.i + dist; 
+		}
+		else {
+			int dist = f.i - dot.y;
+			if (dist < 0) dot.y = f.i + dist; 
+		}
+	}
+}
+
+int main (int argc, char * argv[]) {
+	std::string raw;
+	std::getline(std::ifstream(argv[1]), raw, '\0');
+	std::vector<std::string> parts, strdots, strfolds;
+	split(parts, raw, "\n\n");
+	split(strdots, parts[0], "\n");
+	split(strfolds, parts[1], "\n");
+
+	std::vector<Dot> dots;
+	for (auto strdot : strdots) {
+		std::vector<std::string> xy;
+		split(xy, strdot, ",");
+		dots.emplace_back(
+			std::stoi(xy[0]),
+			std::stoi(xy[1]));
+	}
+
+	std::vector<Fold> folds;
+	for (auto strfold : strfolds) {
+		if (strfold.size() == 0) continue;
+		std::vector<std::string> com;
+		split(com, strfold, "=");
+		folds.emplace_back(
+			com[0] == "fold along x", 
+			std::stoi(com[1]));
+	}
+
+	int iter = folds.size(); 
+	if (argc > 2) iter = atoi(argv[2]);
+	for (Fold f : folds) {
+		fold(dots, f);
+	}
+	show(dots, true);
+
+
+	return 0;
+}
diff --git a/2021/day13/day13_input.txt b/2021/day13/day13_input.txt
new file mode 100644
index 0000000..4d2f146
--- /dev/null
+++ b/2021/day13/day13_input.txt
@@ -0,0 +1,900 @@
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+
+fold along x=655
+fold along y=447
+fold along x=327
+fold along y=223
+fold along x=163
+fold along y=111
+fold along x=81
+fold along y=55
+fold along x=40
+fold along y=27
+fold along y=13
+fold along y=6
diff --git a/2021/day13/day13_input_ez.txt b/2021/day13/day13_input_ez.txt
new file mode 100644
index 0000000..282114c
--- /dev/null
+++ b/2021/day13/day13_input_ez.txt
@@ -0,0 +1,21 @@
+6,10
+0,14
+9,10
+0,3
+10,4
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+6,0
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+4,1
+0,13
+10,12
+3,4
+3,0
+8,4
+1,10
+2,14
+8,10
+9,0
+
+fold along y=7
+fold along x=5
diff --git a/2021/day13/makefile b/2021/day13/makefile
new file mode 100644
index 0000000..02a6cb9
--- /dev/null
+++ b/2021/day13/makefile
@@ -0,0 +1,2 @@
+all day13.cpp:
+	g++ -std=c++20 -o day13 day13.cpp