From 6129705885129c29d311f8664c40f777133e58bc Mon Sep 17 00:00:00 2001
From: Julien Dessaux
Date: Fri, 9 Dec 2022 15:04:28 +0100
Subject: 2022-09 in zig

---
 2022/09-rope-bridge/first.zig | 222 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 222 insertions(+)
 create mode 100644 2022/09-rope-bridge/first.zig

(limited to '2022/09-rope-bridge/first.zig')

diff --git a/2022/09-rope-bridge/first.zig b/2022/09-rope-bridge/first.zig
new file mode 100644
index 0000000..9229f5d
--- /dev/null
+++ b/2022/09-rope-bridge/first.zig
@@ -0,0 +1,222 @@
+const std = @import("std");
+
+const example = @embedFile("example");
+const input = @embedFile("input");
+
+pub fn main() anyerror!void {
+    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+    defer arena.deinit();
+    const allocator = arena.allocator();
+
+    try std.testing.expectEqual(try solve(example, allocator), 13);
+    const result = try solve(input, allocator);
+    try std.io.getStdOut().writer().print("{}\n", .{result});
+}
+
+const Line = struct {
+    data: std.ArrayList(bool),
+    x: i64,
+    fn init(allocator: std.mem.Allocator) !*Line {
+        var l = try allocator.create(Line);
+        l.data = std.ArrayList(bool).init(allocator);
+        return l;
+    }
+    inline fn len(l: Line) usize {
+        return l.data.items.len;
+    }
+    fn set(l: *Line, x: i64) !void {
+        if (l.len() == 0) { // this is en empty line
+            l.x = x;
+            try l.data.append(true);
+            return;
+        }
+        const lx = @intCast(i64, l.len());
+        if (x >= l.x) {
+            if (x < l.x + lx) { // just set the value
+                l.data.items[@intCast(usize, x - l.x)] = true;
+            } else { // we need to add trailing spaces
+                var i: usize = l.len();
+                while (i < x - l.x) : (i += 1) {
+                    try l.data.append(false);
+                }
+                try l.data.append(true);
+            }
+        } else { // we need to shift right and add leading spaces
+            const oldLen = l.len();
+            l.data.items.len += @intCast(usize, l.x - x);
+            try l.data.ensureUnusedCapacity(l.len());
+            std.mem.copyBackwards(bool, l.data.items[@intCast(usize, l.x - x)..], l.data.items[0..oldLen]);
+            l.data.items[0] = true;
+            var i: usize = 1;
+            while (i < @intCast(usize, l.x - x)) : (i += 1) {
+                l.data.items[i] = false;
+            }
+            l.x = x;
+        }
+    }
+    pub fn visited(l: Line) u64 {
+        var tot: u64 = 0;
+        var i: usize = 0;
+        while (i < l.len()) : (i += 1) {
+            if (l.data.items[i]) {
+                tot += 1;
+            }
+        }
+        return tot;
+    }
+};
+
+pub const Field = struct {
+    allocator: std.mem.Allocator,
+    x: i64 = 0,
+    y: i64 = 0,
+    lines: std.ArrayList(*Line),
+    lx: usize = 0,
+    fn init(allocator: std.mem.Allocator) !*Field {
+        var f = try allocator.create(Field);
+        f.allocator = allocator;
+        f.x = undefined;
+        f.y = 0;
+        f.lines = std.ArrayList(*Line).init(allocator);
+        var l = try f.lines.addOne();
+        l.* = try Line.init(allocator);
+        f.lx = 0;
+        return f;
+    }
+    inline fn len(f: Field) usize {
+        return f.lines.items.len;
+    }
+    pub fn set(f: *Field, x: i64, y: i64) !void {
+        if (y >= f.y) {
+            if (y < f.y + @intCast(i64, f.lines.items.len)) { // the line exists
+                try f.lines.items[@intCast(usize, y - f.y)].set(x);
+            } else { // append lines
+                var i: usize = f.lines.items.len;
+                while (i < y - f.y) : (i += 1) {
+                    try f.lines.append(try Line.init(f.allocator));
+                }
+                var l = try Line.init(f.allocator);
+                try l.set(x);
+                try f.lines.append(l);
+            }
+        } else { // preprend lines
+            const oldLen = f.lines.items.len;
+            f.lines.items.len += @intCast(usize, f.y - y);
+            try f.lines.ensureUnusedCapacity(f.lines.items.len);
+            std.mem.copyBackwards(*Line, f.lines.items[@intCast(usize, f.y - y)..], f.lines.items[0..oldLen]);
+            var l = try Line.init(f.allocator);
+            try l.set(x);
+            f.lines.items[0] = l;
+            var i: usize = 1;
+            while (i < @intCast(usize, f.y - y)) : (i += 1) {
+                f.lines.items[i] = try Line.init(f.allocator);
+            }
+            f.y = y;
+        }
+        if (x < f.x or x >= f.x + @intCast(i64, f.lx)) { // recalculate boundaries
+            f.x = std.math.maxInt(i64);
+            var x2: i64 = std.math.minInt(i64);
+            for (f.lines.items) |line| {
+                if (line.len() == 0) continue;
+                if (f.x > line.x) f.x = line.x;
+                if (x2 < line.x + @intCast(i64, line.len())) x2 = line.x + @intCast(i64, line.len());
+            }
+            f.lx = @intCast(usize, x2 - f.x);
+        }
+        return;
+    }
+    pub fn visited(f: Field) u64 {
+        var tot: u64 = 0;
+        var i: usize = 0;
+        while (i < f.len()) : (i += 1) {
+            tot += f.lines.items[i].visited();
+        }
+        return tot;
+    }
+};
+
+const Rope = struct {
+    hx: i64 = 0,
+    hy: i64 = 0,
+    tx: i64 = 0,
+    ty: i64 = 0,
+    fn step(r: *Rope, direction: u8) void {
+        switch (direction) {
+            'D' => {
+                r.hy += 1;
+            },
+            'L' => {
+                r.hx -= 1;
+            },
+            'R' => {
+                r.hx += 1;
+            },
+            'U' => {
+                r.hy -= 1;
+            },
+            else => unreachable,
+        }
+        if (r.tx == r.hx) { // same line
+            if (r.ty + 2 == r.hy) { // to the left
+                r.ty += 1;
+            } else if (r.ty - 2 == r.hy) { // to the right
+                r.ty -= 1;
+            }
+        } else if (r.ty == r.hy) {
+            if (r.tx + 2 == r.hx) { // to the top
+                r.tx += 1;
+            } else if (r.tx - 2 == r.hx) { // to the bottom
+                r.tx -= 1;
+            }
+        } else if (r.tx + 1 == r.hx) { // on the left by one
+            if (r.ty + 2 == r.hy) { // above by two
+                r.tx += 1;
+                r.ty += 1;
+            } else if (r.ty - 2 == r.hy) { // bellow by two
+                r.tx += 1;
+                r.ty -= 1;
+            }
+        } else if (r.tx - 1 == r.hx) { // on the right by one
+            if (r.ty + 2 == r.hy) { // above by two
+                r.tx -= 1;
+                r.ty += 1;
+            } else if (r.ty - 2 == r.hy) { // bellow by two
+                r.tx -= 1;
+                r.ty -= 1;
+            }
+        } else if (r.ty + 1 == r.hy) { // above by one
+            if (r.tx + 2 == r.hx) { // two to the left
+                r.tx += 1;
+                r.ty += 1;
+            } else if (r.tx - 2 == r.hx) { // two to the right
+                r.tx -= 1;
+                r.ty += 1;
+            }
+        } else if (r.ty - 1 == r.hy) { // bellow by one
+            if (r.tx + 2 == r.hx) { // two to the left
+                r.tx += 1;
+                r.ty -= 1;
+            } else if (r.tx - 2 == r.hx) { // two to the right
+                r.tx -= 1;
+                r.ty -= 1;
+            }
+        }
+    }
+};
+
+fn solve(puzzle: []const u8, allocator: std.mem.Allocator) !u64 {
+    var it = std.mem.tokenize(u8, puzzle, "\n");
+    var rope = Rope{};
+    var field = try Field.init(allocator);
+    // process input
+    while (it.next()) |line| {
+        var elts = std.mem.split(u8, line, " ");
+        _ = elts.next() orelse unreachable; // the move word
+        var n = try std.fmt.parseInt(u8, elts.next() orelse unreachable, 10);
+        while (n > 0) : (n -= 1) {
+            rope.step(line[0]);
+            try field.set(rope.tx, rope.ty);
+        }
+    }
+    return field.visited();
+}
-- 
cgit v1.2.3