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const std = @import("std");
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();
const result = try solve(input, 12, allocator);
try std.io.getStdOut().writer().print("{}\n", .{result});
}
fn solve(puzzle: []const u8, width: u8, allocator: std.mem.Allocator) !u64 {
var it = std.mem.tokenize(u8, puzzle, "\n");
var bits = std.ArrayList(u64).init(allocator);
defer bits.deinit();
if (it.next()) |line| {
for (line) |c| {
var v: u8 = 0;
if (c == '1') {
v = 1;
}
try bits.append(v);
}
}
var len: usize = 1;
while (it.next()) |line| : (len += 1) {
for (line) |c, i| {
if (c == '1') {
bits.items[i] += 1;
}
}
}
var gamma: u64 = 0;
var epsilon: u64 = 0;
var i: usize = 0;
while (i < width) : (i += 1) {
gamma <<= 1;
epsilon <<= 1;
if (bits.items[i] > len / 2) {
gamma += 1;
} else {
epsilon += 1;
}
}
return gamma * epsilon;
}
test "solve" {
const example = @embedFile("example");
try std.testing.expectEqual(solve(example, 5, std.testing.allocator), 198);
}
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