パスワード哲学

コード2020日2の出現

タスク：Xのどこに解決する.

X = the number of valid passwords

例入力

1-3 a: abcde
1-3 b: cdefg
2-9 c: ccccccccc

第1部

split ()とregexの比較

1-3 a: abcde

['1-3 a', 'abcde']

['1-3','a', 'abcde']

['1','3','a','abcde']

/(\d+)-(\d+) (\w): (\w+)/g

前のパズルからのヘルパー関数の活用

1-3 a: abcde

2-9 c: ccccccccc

const createRange = (lower, upper) => {
    return new Array(upper - (lower - 1)).fill(0).map((item, index) => index + lower)
}

アルゴリズムの記述

Generate a list of matched capture groups for each line using the regular expression above

Filter that list to only include items where the following operations return 'true'
  Create a range of numbers that span the lower and upper designated boundaries from the first and second captured groups
  Check that list of numbers for the inclusion of a number that is equivalent to the number returned from the following operations:
    Split the password string into an array of characters
      Filter the list of characters to only include characters that match the character specified by this item's policy
      Return the length of the filtered list

Return the length of the filtered list

第2部

わずかに修正された作業アルゴリズムを書く

Generate a list of matched capture groups for each line using the regular expression above

Filter that list to only include items where the following operations return 'true'
  Create a 2-element list containing the lower and upper designated boundaries from the first and second captured groups
  Filter that list to include either 0, 1 or both numbers based on the following operations:
    For each of the two numbers:
      Split the password string into an array of characters
        Remove N characters from the beginning of the list where N = the current number minus 1
          Return true if the first character is the one specified in the policy
    Return true if the filtered list only contains one number
Return the length of the filtered list

実績