62 lines
No EOL
2.8 KiB
Text
62 lines
No EOL
2.8 KiB
Text
\--- Day 7: Some Assembly Required ---
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----------
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This year, Santa brought little Bobby Tables a set of wires and [bitwise logic gates](https://en.wikipedia.org/wiki/Bitwise_operation)! Unfortunately, little Bobby is a little under the recommended age range, and he needs help assembling the circuit.
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Each wire has an identifier (some lowercase letters) and can carry a [16-bit](https://en.wikipedia.org/wiki/16-bit) signal (a number from `0` to `65535`). A signal is provided to each wire by a gate, another wire, or some specific value. Each wire can only get a signal from one source, but can provide its signal to multiple destinations. A gate provides no signal until all of its inputs have a signal.
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The included instructions booklet describes how to connect the parts together: `x AND y -> z` means to connect wires `x` and `y` to an AND gate, and then connect its output to wire `z`.
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For example:
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* `123 -> x` means that the signal `123` is provided to wire `x`.
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* `x AND y -> z` means that the [bitwise AND](https://en.wikipedia.org/wiki/Bitwise_operation#AND) of wire `x` and wire `y` is provided to wire `z`.
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* `p LSHIFT 2 -> q` means that the value from wire `p` is [left-shifted](https://en.wikipedia.org/wiki/Logical_shift) by `2` and then provided to wire `q`.
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* `NOT e -> f` means that the [bitwise complement](https://en.wikipedia.org/wiki/Bitwise_operation#NOT) of the value from wire `e` is provided to wire `f`.
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Other possible gates include `OR` ([bitwise OR](https://en.wikipedia.org/wiki/Bitwise_operation#OR)) and `RSHIFT` ([right-shift](https://en.wikipedia.org/wiki/Logical_shift)). If, for some reason, you'd like to *emulate* the circuit instead, almost all programming languages (for example, [C](https://en.wikipedia.org/wiki/Bitwise_operations_in_C), [JavaScript](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators), or [Python](https://wiki.python.org/moin/BitwiseOperators)) provide operators for these gates.
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For example, here is a simple circuit:
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```
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123 -> x
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456 -> y
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x AND y -> d
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x OR y -> e
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x LSHIFT 2 -> f
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y RSHIFT 2 -> g
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NOT x -> h
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NOT y -> i
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```
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After it is run, these are the signals on the wires:
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```
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d: 72
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e: 507
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f: 492
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g: 114
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h: 65412
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i: 65079
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x: 123
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y: 456
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```
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In little Bobby's kit's instructions booklet (provided as your puzzle input), what signal is ultimately provided to *wire `a`*?
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Your puzzle answer was `46065`.
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\--- Part Two ---
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----------
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Now, take the signal you got on wire `a`, override wire `b` to that signal, and reset the other wires (including wire `a`). What new signal is ultimately provided to wire `a`?
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Your puzzle answer was `14134`.
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Both parts of this puzzle are complete! They provide two gold stars: \*\*
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At this point, all that is left is for you to [admire your Advent calendar](/2015).
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If you still want to see it, you can [get your puzzle input](7/input). |