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// Own twist on https://en.wikipedia.org/wiki/Shunting-yard_algorithm
const std = @import("std");
const aoc = @import("aoc");
const OpType = enum { ADD, MULT, COUNT };
const Op = struct { prio: u32, optype: OpType };
const Item = union(enum) { num: i64, op: OpType };
const op_names = [_][]const u8{ "ADD", "MULT" };
fn printStack(stack: []Item) void {
for (stack) |item| {
switch (item) {
.op => aoc.debugfmt("{s} ", .{op_names[@enumToInt(item.op)]}),
.num => aoc.debugfmt("{} ", .{item.num}),
}
}
aoc.debugfmt("\n", .{});
}
fn parseToken(line: []const u8, i: *usize, depth: *u32, op_prio: []const u32, mathstack: *std.ArrayList(Item), opstack: *std.ArrayList(Op)) !bool {
if (i.* > line.len) {
return false;
} else if (i.* == line.len) {
while (opstack.items.len > 0)
try mathstack.append(Item{ .op = opstack.pop().optype });
} else {
const c = line[i.*];
switch (c) {
'+', '*' => {
const optype = switch (c) {
'+' => OpType.ADD,
'*' => OpType.MULT,
else => unreachable,
};
const prio = depth.* * @enumToInt(OpType.COUNT) + op_prio[@enumToInt(optype)];
while (opstack.items.len > 0 and
opstack.items[opstack.items.len - 1].prio >= prio)
{
try mathstack.append(Item{ .op = opstack.pop().optype });
}
try opstack.append(Op{ .optype = optype, .prio = prio });
},
'(' => depth.* += 1,
')' => depth.* -= 1,
' ' => {},
else => {
// in this case we know that every number is one digit..
// crappy zig parseInt requires span of exact int size
// before we even know the format >:(((
const val = try std.fmt.parseInt(i64, line[i.* .. i.* + 1], 10);
try mathstack.append(Item{ .num = val });
},
}
}
i.* += 1;
return true;
}
fn reduceStack(mathstack: *std.ArrayList(Item), opstack: *std.ArrayList(Op), tmpstack: *std.ArrayList(Item)) !void {
_ = opstack;
while (mathstack.items.len > 0) {
while (mathstack.items[mathstack.items.len - 1] != .op and
tmpstack.items.len > 0)
{
try mathstack.append(tmpstack.pop());
}
if (mathstack.items.len < 3 or mathstack.items[mathstack.items.len - 1] != .op)
break;
const op = mathstack.pop();
// get first arg
if (mathstack.items[mathstack.items.len - 1] != .num) {
try tmpstack.append(op);
continue;
}
const a = mathstack.pop();
// get second arg
if (mathstack.items[mathstack.items.len - 1] != .num) {
try tmpstack.append(op);
try tmpstack.append(a);
continue;
}
const b = mathstack.pop();
const result: i64 = switch (op.op) {
OpType.ADD => a.num + b.num,
OpType.MULT => a.num * b.num,
else => unreachable,
};
try mathstack.append(Item{ .num = result });
}
}
fn printRPN(allocator: std.mem.Allocator, input: []u8, prios: []const u32) !void {
var mathstack = std.ArrayList(Item).init(allocator);
defer mathstack.deinit();
var opstack = std.ArrayList(Op).init(allocator);
defer opstack.deinit();
var lineit = std.mem.tokenize(u8, input, "\n");
while (lineit.next()) |line| {
var depth: u32 = 0;
var i: usize = 0;
while (try parseToken(line, &i, &depth, prios, &mathstack, &opstack)) {}
}
printStack(mathstack.items);
}
fn partProto(allocator: std.mem.Allocator, input: []u8, prios: []const u32) !?[]u8 {
var answer: i64 = 0;
if (aoc.debug) {
aoc.debugfmt("Reverse Polish Notation:\n", .{});
try printRPN(allocator, input, prios);
}
var mathstack = std.ArrayList(Item).init(allocator);
defer mathstack.deinit();
var opstack = std.ArrayList(Op).init(allocator);
defer opstack.deinit();
var tmpstack = std.ArrayList(Item).init(allocator);
defer tmpstack.deinit();
var lineit = std.mem.tokenize(u8, input, "\n");
while (lineit.next()) |line| {
var depth: u32 = 0;
var i: usize = 0;
while (try parseToken(line, &i, &depth, prios, &mathstack, &opstack)) {
try reduceStack(&mathstack, &opstack, &tmpstack);
}
if (mathstack.items.len != 1) return aoc.Error.InvalidInput;
const last = mathstack.items[mathstack.items.len - 1];
if (last != .num) return aoc.Error.InvalidInput;
answer += last.num;
try mathstack.resize(0);
try opstack.resize(0);
try tmpstack.resize(0);
}
return try std.fmt.allocPrint(allocator, "{}", .{answer});
}
fn part1(allocator: std.mem.Allocator, input: []u8, args: [][]u8) !?[]u8 {
_ = args;
const prios = [_]u32{ 1, 1 };
return try partProto(allocator, input, prios[0..]);
}
fn part2(allocator: std.mem.Allocator, input: []u8, args: [][]u8) !?[]u8 {
_ = args;
const prios = [_]u32{ 2, 1 };
return try partProto(allocator, input, prios[0..]);
}
test "unions" {
const item1 = Item{ .op = OpType.MULT };
const item2 = Item{ .num = 1000 };
const expect = std.testing.expect;
expect(item1 == .op);
expect(item2 == .num);
}
pub const main = aoc.main(part1, part2, .{ "5783053349377", "74821486966872" });
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