likes.js

in about Dev on Algorithm

Codewars 알고리즘 풀이


Problem

  • You probably know the ‘like’ system from Facebook.
    • Facebook의 ‘like’ 시스템을 알고 있을 것이다.
  • We want to create the text that should be displayed next to such an item.
    • 옆에 표시할 텍스트를 작성하려고 한다.
  • Implement a function, which must take in input array, containing the names of people who like an item.
    • like를 누른 사람들의 이름을 포함하는 배열을 가져오는 함수를 작성한다.
  • For 4 more names, the number in ‘and 2 others’ simply increases.
    • 이름이 4개 이상인 경우, ‘and 2 others’와 같이 단순히 증가시킨다.


For example

likes([]) => no one likes this

likes([‘Sam’]) => Sam likes this

likes([‘Ralph’, ‘Lauren’]) => Ralph and Lauren like this

likes([‘Ralph’, ‘Lauren’, ‘Leo’]) => Ralph, Lauren and Leo like this

likes([‘Sam’, ‘Ralph’, ‘Lauren’, ‘Leo’]) => Sam, Ralph and 2 others like this



Solution 01

function likes(arr) {
  if (arr.length === 0) return 'no one likes this';
  if (arr.length === 1) return arr[0] + ' likes this';
  if (arr.length === 2) return arr[0] + ' and ' + arr[1] + ' like this';
  if (arr.length === 3) return arr[0] + ', ' + arr[1] + ' and ' + arr[2] + ' like this';
  return arr[0] + ', ' + arr[1] + ' and ' + (arr.length - 2) + ' others like this';
}

likes([]);                                 // no one likes this
likes(['Sam']);                            // Sam likes this
likes(['Ralph', 'Lauren']);                // Ralph and Lauren like this
likes(['Ralph', 'Lauren', 'Leo']);         // Ralph, Lauren and Leo like this
likes(['Sam', 'Ralph', 'Lauren', 'Leo']);  // Sam, Ralph and 2 others like this


Solution 02

function likes(arr) {
  switch(arr.length) {
    case 0:
      return 'no one likes this';
    case 1:
      return `${arr[0]} likes this`;
    case 2:
      return `${arr[0]} and ${arr[1]} like this`;
    case 3:
      return `${arr[0]}, ${arr[1]} and ${arr[2]} like this`;
    default:
      return `${arr[0]}, ${arr[1]} and ${arr.length - 2} others like this`;
  }
}

likes([]);                                 // no one likes this
likes(['Sam']);                            // Sam likes this
likes(['Ralph', 'Lauren']);                // Ralph and Lauren like this
likes(['Ralph', 'Lauren', 'Leo']);         // Ralph, Lauren and Leo like this
likes(['Sam', 'Ralph', 'Lauren', 'Leo']);  // Sam, Ralph and 2 others like this


Solution 03

function likes(arr) {
  return {
    0: 'no one likes this',
    1: `${arr[0]} likes this`,
    2: `${arr[0]} and ${arr[1]} like this`,
    3: `${arr[0]}, ${arr[1]} and ${arr[2]} like this`,
    4: `${arr[0]}, ${arr[1]} and ${arr.length - 2} others like this`,
  }[Math.min(4, arr.length)];
}

likes([]);                                 // no one likes this
likes(['Sam']);                            // Sam likes this
likes(['Ralph', 'Lauren']);                // Ralph and Lauren like this
likes(['Ralph', 'Lauren', 'Leo']);         // Ralph, Lauren and Leo like this
likes(['Sam', 'Ralph', 'Lauren', 'Leo']);  // Sam, Ralph and 2 others like this