diff --git a/12/input b/12/input
new file mode 100644
index 0000000..84a1558
--- /dev/null
+++ b/12/input
@@ -0,0 +1,24 @@
+hl-WP
+vl-fo
+vl-WW
+WP-start
+vl-QW
+fo-wy
+WW-dz
+dz-hl
+fo-end
+VH-fo
+ps-vl
+FN-dz
+WP-ps
+ps-start
+WW-hl
+end-QW
+start-vl
+WP-fo
+end-FN
+hl-QW
+WP-dz
+QW-fo
+QW-dz
+ps-dz
\ No newline at end of file
diff --git a/12/part1.zig b/12/part1.zig
new file mode 100644
index 0000000..0bc5c20
--- /dev/null
+++ b/12/part1.zig
@@ -0,0 +1,130 @@
+const std = @import("std");
+const print = std.debug.print;
+
+const Node = []const u8;
+const Route = std.ArrayList(Node);
+const Edge = struct {
+    left: Node,
+    right: Node
+};
+
+fn contains(list: []Node, x: Node) bool {
+    for (list) |node| {
+        if (std.mem.eql(u8, node, x)) {
+            return true;
+        }
+    }
+    return false;
+}
+
+fn getOther(edge: Edge, node: Node) ?Node {
+    if (std.mem.eql(u8, edge.left, node)) {
+        return edge.right;
+    }
+    if (std.mem.eql(u8, edge.right, node)) {
+        return edge.left;
+    }
+    return null;
+}
+
+fn isSmol(node: Node) bool {
+    for (node) |rune| {
+        if (!std.ascii.isLower(rune)) return false;
+    }
+
+    return true;
+}
+
+pub fn main() !void {
+    var alloc = std.heap.GeneralPurposeAllocator(.{}){};
+    defer std.debug.assert(!alloc.deinit());
+    var gpa = &alloc.allocator;
+
+    const stdin = std.io.getStdIn().reader();
+
+    var res: u32 = 0;
+
+    var edges = std.ArrayList(Edge).init(gpa);
+    defer edges.deinit();
+
+    var input = try stdin.readAllAlloc(gpa, 4096);
+    defer gpa.free(input);
+
+    var lines = std.mem.split(input, "\n");
+    while (lines.next()) |line| {
+        var it = std.mem.split(line, "-");
+        var left = it.next() orelse unreachable;
+        var right = it.next() orelse unreachable;
+
+        try edges.append(Edge{
+            .left = left,
+            .right = right,
+        });
+    }
+
+    var routes = std.ArrayList(Route).init(gpa);
+    defer {
+        for (routes.items) |route| {
+            route.deinit();
+        }
+        routes.deinit();
+    }
+    {
+        var route = Route.init(gpa);
+        try route.append("start");
+        try routes.append(route);
+    }
+
+    // var x: u8 = 0;
+
+    while (true) {
+        var cont = false;
+
+        var newRoutes = std.ArrayList(Route).init(gpa);
+        defer newRoutes.deinit();
+
+        var stale = std.ArrayList(usize).init(gpa);
+        defer stale.deinit();
+
+        // print("Routes ({}):\n", .{routes.items.len});
+        // for (routes.items) |route| {
+        //     print("{s}\n", .{route.items});
+        // }
+
+        for (routes.items) |route, i| {
+            const last = route.items[route.items.len - 1];
+            if (std.mem.eql(u8, last, "end")) {
+                continue;
+            }
+            cont = true;
+            try stale.append(i);
+
+            for (edges.items) |edge| {
+                if (getOther(edge, last)) |other| {
+                    // print("> {s}\n", .{other});
+                    if (isSmol(other) and contains(route.items, other)) {
+                        continue;
+                    } else {
+                        var newRoute = Route.init(gpa);
+                        try newRoute.appendSlice(route.items);
+                        try newRoute.append(other);
+                        // print("new route: {s}\n", .{newRoute.items});
+                        try newRoutes.append(newRoute);
+                    }
+                }
+            }
+        }
+
+        var i: usize = 0;
+        while (i < stale.items.len) : (i += 1) {
+            var route = routes.orderedRemove(stale.items[stale.items.len-1-i]);
+            route.deinit();
+        }
+
+        try routes.appendSlice(newRoutes.items);
+
+        if (!cont) break;
+    }
+
+    std.debug.print("{}\n", .{routes.items.len});
+}
diff --git a/12/part2.zig b/12/part2.zig
new file mode 100644
index 0000000..f0573c7
--- /dev/null
+++ b/12/part2.zig
@@ -0,0 +1,169 @@
+const std = @import("std");
+const print = std.debug.print;
+
+const Node = u16;
+const Route = []Node;
+const Edge = struct {
+    left: Node,
+    right: Node
+};
+
+const START_NODE = 0x0000;
+const END_NODE = 0xffff;
+
+fn parseNode(input: []const u8) Node {
+    if (std.mem.eql(u8, input, "start")) return START_NODE;
+    if (std.mem.eql(u8, input, "end")) return END_NODE;
+    if (input.len == 1) return @intCast(u16, input[0]) << 8 | 0x20;
+    return @intCast(u16, input[0]) << 8 | input[1];
+}
+
+fn isThereASmolDuplicate(list: []Node) bool {
+    for (list) |node| {
+        if (isSmol(node) and count(list, node) > 1) {
+            return true;
+        }
+    }
+    return false;
+}
+
+fn count(list: []Node, x: Node) u32 {
+    var res: u32 = 0;
+    for (list) |node| {
+        if (node == x) {
+            res += 1;
+            if (res == 2) {
+                return 2;
+            }
+        }
+    }
+    return res;
+}
+
+fn isForbiddenSmol(list: []Node, x: Node) bool {
+    if (isThereASmolDuplicate(list)) {
+        for (list) |node| {
+            if (node == x) {
+                return true;
+            }
+        }
+        return false;
+    } else if (x == START_NODE) {
+        return true;
+    } else {
+        return count(list, x) > 1;
+    }
+}
+
+fn getOther(edge: Edge, node: Node) ?Node {
+    if (edge.left == node) {
+        return edge.right;
+    }
+    if (edge.right == node) {
+        return edge.left;
+    }
+    return null;
+}
+
+fn isSmol(node: Node) bool {
+    return (node & 0x2020) == 0x2020 or node == START_NODE or node == END_NODE;
+}
+
+pub fn main() !void {
+    var alloc = std.heap.GeneralPurposeAllocator(.{}){};
+    defer std.debug.assert(!alloc.deinit());
+    var gpa = &alloc.allocator;
+
+    const stdin = std.io.getStdIn().reader();
+
+    var res: u32 = 0;
+
+    var edges = std.ArrayList(Edge).init(gpa);
+    defer edges.deinit();
+
+    var input = try stdin.readAllAlloc(gpa, 4096);
+    defer gpa.free(input);
+
+    var lines = std.mem.split(input, "\n");
+    while (lines.next()) |line| {
+        var it = std.mem.split(line, "-");
+        var left = it.next() orelse unreachable;
+        var right = it.next() orelse unreachable;
+        var leftInt = parseNode(left);
+        var rightInt = parseNode(right);
+
+        try edges.append(Edge{
+            .left = leftInt,
+            .right = rightInt,
+        });
+    }
+
+    var routes = std.ArrayList(Route).init(gpa);
+    defer {
+        for (routes.items) |route| {
+            gpa.free(route);
+        }
+        routes.deinit();
+    }
+    {
+        var route = try gpa.alloc(Node, 1);
+        route[0] = START_NODE;
+        try routes.append(route);
+    }
+
+    var x: u8 = 0;
+
+    while (x < 1000) : (x += 1) {
+        var cont = false;
+
+        var newRoutes = std.ArrayList(Route).init(gpa);
+        defer newRoutes.deinit();
+
+        var stale = std.ArrayList(usize).init(gpa);
+        defer stale.deinit();
+
+        // print("Routes ({}):\n", .{routes.items.len});
+        // for (routes.items) |route| {
+        //     print("{any}\n", .{route.items});
+        // }
+
+        for (routes.items) |route, i| {
+            const last = route[route.len - 1];
+            if (last == END_NODE) {
+                continue;
+            }
+            cont = true;
+            try stale.append(i);
+
+            for (edges.items) |edge| {
+                if (getOther(edge, last)) |other| {
+                    // print("> {s}\n", .{other});
+                    if (isSmol(other) and isForbiddenSmol(route, other)) {
+                        continue;
+                    } else {
+                        var newRoute = try gpa.alloc(Node, route.len+1);
+                        std.mem.copy(Node, newRoute, route);
+                        newRoute[route.len] = other;
+                        // print("new route: {s}\n", .{newRoute.items});
+                        try newRoutes.append(newRoute);
+                    }
+                }
+            }
+        }
+
+        // print("Removed routes: {}\n", .{stale.items.len});
+        // print("Added routes: {}\n", .{newRoutes.items.len});
+
+        var i: usize = 0;
+        while (i < stale.items.len) : (i += 1) {
+            var route = routes.swapRemove(stale.items[stale.items.len-1-i]);
+            gpa.free(route);
+        }
+
+        try routes.appendSlice(newRoutes.items);
+
+        if (!cont) break;
+    }
+
+    std.debug.print("{}\n", .{routes.items.len});
+}
diff --git a/12/testinput b/12/testinput
new file mode 100644
index 0000000..898cd56
--- /dev/null
+++ b/12/testinput
@@ -0,0 +1,7 @@
+start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end
\ No newline at end of file