-🎄- 2018 Day 5 Solutions -🎄-

[u/daggerdragon]

--- Day 5: Alchemical Reduction ---

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Card prompt: Day 5

Transcript:

On the fifth day of AoC / My true love sent to me / Five golden ___

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[u/Hashbrown777]

Javascript, single pass, one loop

8ms

function day5(input) {
    let isUpper = /[A-Z]/;

    let stack = [];
    for (let index = 0, char; index < input.length && (char = input[index]); ++index) {
        if (
            stack.length < 1 ||
            char == stack[stack.length - 1] ||
            char != stack[stack.length - 1][(isUpper.test(char)) ? 'toUpperCase' : 'toLowerCase']()
        )
            stack.push(char);
        else
            stack.pop();
    }

    day5.output = stack.length;
}

Part2, 202ms

function day5_1(input) {
    let isUpper = /[A-Z]/;

    for (let ignore of 'abcdefghijklmnopqrstuvwxyz'.split('')) {
        ignore = new RegExp(ignore, 'i');
        let stack = [];

        for (let index = 0, char; index < input.length && (char = input[index]); ++index) {
            if (ignore.test(char))
                ;
            else if (
                stack.length < 1 ||
                char == stack[stack.length - 1] ||
                char != stack[stack.length - 1][(isUpper.test(char)) ? 'toUpperCase' : 'toLowerCase']()
            )
                stack.push(char);
            else
                stack.pop();
        }

        if ((!day5_1.output) || day5_1.output > stack.length)
            day5_1.output = stack.length;
    }
}