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const std = @import("std");
pub fn parse(_: std.mem.Allocator, data: []const u8) ![]const u8 {
return data;
}
pub fn part1(_: std.mem.Allocator, input: []const u8) !u32 {
var state: enum { m, u, l, lp, lhs, rhs } = .m;
var lhs: u32 = 0;
var rhs: u32 = 0;
var sum: u32 = 0;
for (input) |c| {
if (state == .m and c == 'm') {
state = .u;
} else if (state == .u and c == 'u') {
state = .l;
} else if (state == .l and c == 'l') {
state = .lp;
} else if (state == .lp and c == '(') {
state = .lhs;
} else if (state == .lhs and '0' <= c and c <= '9') {
lhs *= 10;
lhs += c - '0';
} else if (state == .lhs and c == ',') {
state = .rhs;
} else if (state == .rhs and '0' <= c and c <= '9') {
rhs *= 10;
rhs += c - '0';
} else if (state == .rhs and c == ')') {
state = .m;
sum += lhs * rhs;
lhs = 0;
rhs = 0;
} else {
lhs = 0;
rhs = 0;
state = .m;
}
}
return sum;
}
test "part 2" {
std.debug.assert(try part2(undefined, "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))") == 48);
}
pub fn part2(_: std.mem.Allocator, input: []const u8) !u32 {
var sum: u32 = 0;
var i: usize = 0;
while (i < input.len) : (i += 1) {
const mul = std.mem.indexOfPos(u8, input, i, "mul(") orelse input.len;
const dont = std.mem.indexOfPos(u8, input, i, "don't()") orelse input.len;
i = @min(mul, dont);
if (i == input.len) break;
if (i == mul) {
i += 4;
var lhs: u32 = 0;
while ('0' <= input[i] and input[i] <= '9') : (i += 1) {
lhs = lhs * 10 + input[i] - '0';
}
if (input[i] != ',') continue;
i += 1;
var rhs: u32 = 0;
while ('0' <= input[i] and input[i] <= '9') : (i += 1) {
rhs = rhs * 10 + input[i] - '0';
}
if (input[i] != ')') continue;
std.debug.print("sum += mul({},{})\n", .{ lhs, rhs });
sum += lhs * rhs;
} else {
std.debug.assert(i == dont);
const do = std.mem.indexOfPos(u8, input, i, "do()") orelse break;
i = do + 3;
}
}
return sum;
}
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