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在给定完整数组的情况下,如何识别不完整数组中缺少哪些元素?

purely-functional functional-programming arrays javascript

1

GirkovArpa · 技术社区 · 6 年前

我正试图为这个问题写一个实用的解决方案。我已经有了一个解决方案,它使用循环和无递归的变异(我知道我下面尝试的是变异,我正试图避免这种情况)。

请在下面的注释中查看预期输出。我要强调的是,元素不一定是唯一的,排序也不重要。

const getNamesWhichFillHoles = (namesArrayWithHoles, namesArrayFilled, fillers = []) => {
  const holey = [...namesArrayWithHoles].filter(Boolean);
  const filled = [...namesArrayFilled].filter(Boolean);
  const fillerIndexInFilled = filled.findIndex(name => !holey.includes(name));
  if (fillerIndexInFilled === -1) return fillers;
  const filler = filled[fillerIndexInFilled];
  const fillerIndexInHoley = holey.findIndex(name => name == filler);
  fillers.push(filler);
  filled[fillerIndexInFilled] = null;
  holey[fillerIndexInHoley] = null;
  return getNamesWhichFillHoles(holey, filled, fillers);
}

const namesArrayWithHoles = ['Bob', null, null, 'Sue', null];
const namesArrayFilled = ['Jim', 'Bob', 'Bob', 'Sam', 'Sue',];
const fillerNames = getNamesWhichFillHoles(namesArrayWithHoles, namesArrayFilled);

console.log(fillerNames); // [ 'Jim', 'Sam' ]
// should be: [ 'Jim', 'Sam', 'Bob' ]

2 回复 | 直到 6 年前

1

Gorisanson John Kugelman 6 年前

您可以执行以下操作:

const namesArrayWithHoles = ['Bob', null, null, 'Sue', null];
const namesArrayFilled = ['Jim', 'Bob', 'Bob', 'Sam', 'Sue'];

const result = namesArrayFilled.reduce(
  (acc, elem) => {
    const index = acc[0].indexOf(elem);
    if (index != -1) {
      return [acc[0].slice(0, index).concat(acc[0].slice(index + 1)), acc[1]];
    }
    return [acc[0], acc[1].concat(elem)];
  },
  [namesArrayWithHoles, []]
)[1];

console.log(result);

2

0

GirkovArpa 6 年前

我找到了这个解决方案。它确实假设没有 null 因为那只是分散注意力。

const getMissingValues = (partial, complete) => {
  const equals = a => b => b == a;
  const push = (arr, val, count) => count ? push([...arr, val], val, count - 1) : [...arr];
  return [...new Set(complete)].reduce((missing, val) => {
    const { length: a } = partial.filter(equals(val));
    const { length: b } = complete.filter(equals(val));
    const diff = (b - a);
    return push(missing, val, diff);
  }, []);
}

const partial = ['Bob', 'Sue'];
const complete = ['Jim', 'Bob', 'Bob', 'Bob', 'Sue', 'Sue', 'Sam'];
const missing = getMissingValues(partial, complete);

console.log(missing); // [ 'Jim', 'Bob', 'Bob', 'Sue', 'Sam' ]