Created Trie

1 files changed, 81 insertions, 0 deletions

diff --git a/src/trie.zig b/src/trie.zig
new file mode 100644
index 0000000..ee77954
--- /dev/null
+++ b/src/trie.zig
@@ -0,0 +1,81 @@
+const std = @import("std");
+const mem = std.mem;
+
+pub const Color = enum { red, blue };
+
+pub const Node = struct {
+    children: [256]?*Node = [_]?*Node{null} ** 256,
+    value: ?Color = null,
+};
+
+pub const Trie = struct {
+    allocator: mem.Allocator,
+    root: Node,
+    node_count: usize = 0,
+
+    fn asBytes(cp: u24) []const u8 {
+        const bytes: [3]u8 = @bitCast(cp);
+
+        return if (bytes[0] < 128)
+            bytes[0..1]
+        else if (bytes[1] == 0)
+            bytes[0..1]
+        else if (bytes[2] == 0)
+            bytes[0..2]
+        else
+            bytes[0..];
+    }
+
+    pub fn put(self: *Trie, cp: u24, v: Color) !void {
+        const s = asBytes(cp);
+        var current: *Node = &self.root;
+
+        for (s, 0..) |b, i| {
+            if (current.children[b]) |n| {
+                if (i == s.len - 1) {
+                    n.value = v;
+                    return;
+                }
+
+                current = n;
+                continue;
+            }
+
+            self.node_count += 1;
+            const new_node = try self.allocator.create(Node);
+            new_node.* = .{ .value = if (i == s.len - 1) v else null };
+            current.children[b] = new_node;
+            current = new_node;
+        }
+    }
+
+    pub fn get(self: Trie, cp: u24) ?Color {
+        const s = asBytes(cp);
+        var current = &self.root;
+
+        return for (s, 0..) |b, i| {
+            if (current.children[b]) |n| {
+                if (i == s.len - 1) break if (n.value) |v| v else null;
+                current = n;
+            }
+        } else null;
+    }
+};
+
+test "Trie works" {
+    var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
+    defer arena.deinit();
+    const allocator = arena.allocator();
+
+    var trie = Trie{ .allocator = allocator, .root = .{} };
+
+    const cp_1: u21 = '\u{10ffff}';
+    const cp_2: u21 = '\u{10ff}';
+    const cp_3: u21 = '\u{10}';
+
+    try trie.put(cp_1, .red);
+    try trie.put(cp_3, .blue);
+    try std.testing.expectEqual(@as(?Color, .red), trie.get(cp_1));
+    try std.testing.expectEqual(@as(?Color, null), trie.get(cp_2));
+    try std.testing.expectEqual(@as(?Color, .blue), trie.get(cp_3));
+}