isValidWalk.js

in about Dev on Algorithm

Codewars 알고리즘 풀이


Problem

  • You live in the city of Cartesia where all roads are laid out in a perfect grid.
    • 당신은 모든 도로가 완벽한 격자(grid)에 배치된 Cartesia city에 살고 있다.
  • You arrived ten minutes too early to an appointment, so you decided to take the opportunity to go for a short walk.
    • 약속에 10분 일찍 도착해서 잠시 걷기로 했다.
  • The city provides its citizens with a Walk Generating App on their phones everytime you press the button it sends you an array of one-letter strings representing directions to walk (eg. [‘n’, ‘s’, ‘w’, ‘e’]).
    • 이 city는 시민들에게 Walk Generating App을 제공한다.
    • 버튼을 누를 때마다 걷는 방향을 나타내는 하나의 문자열 배열이 전송된다.
    • [‘n’, ‘s’, ‘w’, ‘e’] (North, South, West, East)
  • You always walk only a single block in a direction and you know it takes you one minute to traverse one city block, so create a function that will return ‘true’ if the walk the app gives you will take you exactly ten minutes and will return you to your starting point.
    • 하나의 block을 통과하는 데 1분이 걸린다.
    • 출발점으로 돌아가는 데 10분이 걸리면 ‘true’를 반환한다.
  • Return ‘false’ otherwise.
    • 그렇지 않으면 ‘false’를 반환한다.



Solution 01

function isValidWalk(arr) {
  const north = arr.filter((i) => i === 'n').length;
  const south = arr.filter((i) => i === 's').length;
  const west = arr.filter((i) => i === 'w').length;
  const east = arr.filter((i) => i === 'e').length;
  
  return arr.length === 10 && north === south && west === east;
}

isValidWalk(['n', 'n', 'n', 'n', 'n', 'n', 'n', 'n', 'n', 'n']);  // false
isValidWalk(['n', 'n', 'n', 'n', 'n', 's', 's', 's', 's', 's']);  // true
isValidWalk(['n', 's', 'n', 's', 'n', 's', 'n', 's', 'n', 's']);  // true
isValidWalk(['n', 'e', 's', 'w', 'n', 'w', 's', 'e', 's', 'n']);  // true
isValidWalk(['n']);  // false


Solution 02

function isValidWalk(arr) {
  let distanceY = 0;
  let distanceX = 0;
  
  for (let i = 0; i < arr.length; i++) {
    switch(arr[i]) {
      case 'n':
        distanceY++;
        break;
      case 's':
        distanceY--;
        break;
      case 'w':
        distanceX--;
        break;
      case 'e':
        distanceX++;
        break;
    }
  }
  
  return arr.length === 10 && distanceY === 0 && distanceX === 0;
}

isValidWalk(['n', 'n', 'n', 'n', 'n', 'n', 'n', 'n', 'n', 'n']);  // false
isValidWalk(['n', 'n', 'n', 'n', 'n', 's', 's', 's', 's', 's']);  // true
isValidWalk(['n', 's', 'n', 's', 'n', 's', 'n', 's', 'n', 's']);  // true
isValidWalk(['n', 'e', 's', 'w', 'n', 'w', 's', 'e', 's', 'n']);  // true
isValidWalk(['n']);  // false


Solution 03

function isValidWalk(arr) {
  let obj = {
    n: 0,
    s: 0,
    w: 0,
    e: 0
  };
  
  arr.forEach((i) => obj[i]++);
  
  return arr.length === 10 && obj.n === obj.s && obj.w === obj.e;
}

isValidWalk(['n', 'n', 'n', 'n', 'n', 'n', 'n', 'n', 'n', 'n']);  // false
isValidWalk(['n', 'n', 'n', 'n', 'n', 's', 's', 's', 's', 's']);  // true
isValidWalk(['n', 's', 'n', 's', 'n', 's', 'n', 's', 'n', 's']);  // true
isValidWalk(['n', 'e', 's', 'w', 'n', 'w', 's', 'e', 's', 'n']);  // true
isValidWalk(['n']);  // false