freeCodeCamp/curriculum/challenges/chinese/02-javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/diff-two-arrays.md

id, title, challengeType, forumTopicId, dashedName

id	title	challengeType	forumTopicId	dashedName
a5de63ebea8dbee56860f4f2	数组的对称差	5	16008	diff-two-arrays

--description--

在这道题目中，我们需要实现一个函数，它可以比较两个输入数组并返回一个新数组；返回的新数组需包含传入的两个数组中，仅在一个数组里出现的元素。如果某个元素同时出现在两个数组中，则不应包含在返回的数组里。换言之，我们需要返回两个数组的对称差。

注意：
返回数组中的元素顺序不会影响挑战是否通过。

--hints--

diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]) 应返回一个数组。

assert(typeof diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]) === 'object');

["diorite", "andesite", "grass", "dirt", "pink wool", "dead shrub"], ["diorite", "andesite", "grass", "dirt", "dead shrub"] 应返回 ["pink wool"]。

assert.sameMembers(
  diffArray(
    ['diorite', 'andesite', 'grass', 'dirt', 'pink wool', 'dead shrub'],
    ['diorite', 'andesite', 'grass', 'dirt', 'dead shrub']
  ),
  ['pink wool']
);

["diorite", "andesite", "grass", "dirt", "pink wool", "dead shrub"], ["diorite", "andesite", "grass", "dirt", "dead shrub"] 应返回一个长度为 1 的数组。

assert(
  diffArray(
    ['diorite', 'andesite', 'grass', 'dirt', 'pink wool', 'dead shrub'],
    ['diorite', 'andesite', 'grass', 'dirt', 'dead shrub']
  ).length === 1
);

["andesite", "grass", "dirt", "pink wool", "dead shrub"], ["diorite", "andesite", "grass", "dirt", "dead shrub"] 应返回 ["diorite", "pink wool"]。

assert.sameMembers(
  diffArray(
    ['andesite', 'grass', 'dirt', 'pink wool', 'dead shrub'],
    ['diorite', 'andesite', 'grass', 'dirt', 'dead shrub']
  ),
  ['diorite', 'pink wool']
);

["andesite", "grass", "dirt", "pink wool", "dead shrub"], ["diorite", "andesite", "grass", "dirt", "dead shrub"] 应返回一个长度为 2 的数组。

assert(
  diffArray(
    ['andesite', 'grass', 'dirt', 'pink wool', 'dead shrub'],
    ['diorite', 'andesite', 'grass', 'dirt', 'dead shrub']
  ).length === 2
);

["andesite", "grass", "dirt", "dead shrub"], ["andesite", "grass", "dirt", "dead shrub"] 应返回 []。

assert.sameMembers(
  diffArray(
    ['andesite', 'grass', 'dirt', 'dead shrub'],
    ['andesite', 'grass', 'dirt', 'dead shrub']
  ),
  []
);

["andesite", "grass", "dirt", "dead shrub"], ["andesite", "grass", "dirt", "dead shrub"] 应返回一个空数组。

assert(
  diffArray(
    ['andesite', 'grass', 'dirt', 'dead shrub'],
    ['andesite', 'grass', 'dirt', 'dead shrub']
  ).length === 0
);

[1, 2, 3, 5], [1, 2, 3, 4, 5] 应返回 [4]。

assert.sameMembers(diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]), [4]);

[1, 2, 3, 5], [1, 2, 3, 4, 5] 应返回一个长度为 1 的数组。

assert(diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]).length === 1);

[1, "calf", 3, "piglet"], [1, "calf", 3, 4] 应返回 ["piglet", 4]。

assert.sameMembers(diffArray([1, 'calf', 3, 'piglet'], [1, 'calf', 3, 4]), [
  'piglet',
  4
]);

[1, "calf", 3, "piglet"], [1, "calf", 3, 4] 应返回一个长度为 2 的数组。

assert(diffArray([1, 'calf', 3, 'piglet'], [1, 'calf', 3, 4]).length === 2);

[], ["snuffleupagus", "cookie monster", "elmo"] 应返回 ["snuffleupagus", "cookie monster", "elmo"]。

assert.sameMembers(diffArray([], ['snuffleupagus', 'cookie monster', 'elmo']), [
  'snuffleupagus',
  'cookie monster',
  'elmo'
]);

[], ["snuffleupagus", "cookie monster", "elmo"] 应返回一个长度为 3 的数组。

assert(diffArray([], ['snuffleupagus', 'cookie monster', 'elmo']).length === 3);

[1, "calf", 3, "piglet"], [7, "filly"] 应返回 [1, "calf", 3, "piglet", 7, "filly"]。

assert.sameMembers(diffArray([1, 'calf', 3, 'piglet'], [7, 'filly']), [
  1,
  'calf',
  3,
  'piglet',
  7,
  'filly'
]);

[1, "calf", 3, "piglet"], [7, "filly"] 应返回一个长度为 6 的数组。

assert(diffArray([1, 'calf', 3, 'piglet'], [7, 'filly']).length === 6);

--seed--

--seed-contents--

function diffArray(arr1, arr2) {
  var newArr = [];
  return newArr;
}

diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]);

--solutions--

function diffArray(arr1, arr2) {
  var newArr = [];
  var h1 = Object.create(null);
  arr1.forEach(function(e) {
    h1[e] = e;
  });

  var h2 = Object.create(null);
  arr2.forEach(function(e) {
    h2[e] = e;
  });

  Object.keys(h1).forEach(function(e) {
     if (!(e in h2)) newArr.push(h1[e]);
  });
  Object.keys(h2).forEach(function(e) {
     if (!(e in h1)) newArr.push(h2[e]);
  });
  return newArr;
}