2.7Recursion-Practice 2

이전 포스팅에서 배운 재귀 알고리즘을 추가적으로 연습해보자.

예시 5: capitalizeWords

Write a recursive function called capitalizeWords. Given an array of strings, capitalize all the letters of the strings in the array.

javascript
function capitalizeWords(array){
  if(array.length === 1){
    return [array[0].toUpperCase()];
  }
  let res = capitalizeWords(array.slice(0, -1));
  res.push(array.slice(array.length - 1)[0].toUpperCase());
  return res;
}

예시 6: nestedEvenSum

Write a recursive function called nestedEvenSum. Return the sum of all even numbers in an object which may contain nested objects.

javascript
function nestedEvenSum(obj, sum = 0){
  for(let key in obj){
    if(typeof obj[key] === 'object'){
      sum += nestedEvenSum(obj[key]);
    } else if(typeof obj[key] === 'number' && obj[key] % 2 === 0){
      sum += obj[key];
    }
  }
  return sum;
}

예시 7: stringifyNumbers

Write a function called stringifyNumbers which takes in an object and finds all of the values which are numbers and converts them to strings. Recursion would be a great way to solve this!

The exercise intends for you to create a new object with the numbers converted to strings, and not modify the original. Keep the original object unchanged.

javascript
function stringifyNumbers(obj){
  const newObj = {};
  for(let key in obj){
    if(typeof obj[key] === 'number'){
      newObj[key] = obj[key].toString();
    } else if (typeof obj[key] === 'object' && !Array.isArray(obj[key])){
      newObj[key] = stringifyNumbers(obj[key])
    } else {
      newObj[key] = obj[key]
    }
  }
  return newObj;
}

예시 8: collectStrings

Write a function called collectStrings which accepts an object and returns an array of all the values in the object that have a typeof string

javascript
function collectStrings(obj){
  const stringsArr = [];
  for(let key in obj){
    if(typeof obj[key] === 'string'){
      stringsArr.push(obj[key]);
    } else if(typeof obj[key] === 'object'){
      stringsArr = stringsArr.concat(collectStrings[obj[key]]);
    }
  }
  return stringsArr;
}

나는 이렇게 풀었다. push 메소드를 쓸 거면 배열을 펼쳐서 넣고, 그렇지 않으면 concat으로 합쳐야 한다.

javascript
function collectStrings(obj){
    const collection = [];
    for(let key in obj){
        if(typeof obj[key] === 'object' && !Array.isArray(obj[key])){
            collection.push(...collectStrings(obj[key]))
        } else if(typeof obj[key] === 'string'){
            collection.push(obj[key])
        } else console.log(obj[key])
    }
    return collection;
}