检查数组中两个不同数字的总和是否等于一个可变数字? [英] Check if the sum of two different numbers in an array equal a variable number?

问题描述

在Ruby中，我想获取一个数字数组，选择2个不同的数字，将这2个数字加在一起，然后查看那里的天气等于变量x.y和变量x.这是我使用的代码

In Ruby, I would like to take an array of numbers, select 2 different numbers, add those 2 numbers together and see weather there equal to a variable x.y'd a variable x. Here is the code I used

def arrayIsEqual? (numArray, x)
  return true if numArray.sample + numArray.sample == x
  return false if numArray.empty? || numArray.count == 1
end

例如

numArray = [4,2,7,5]
x = 11

arrayIsEqual (numArray, n)应该返回true，因为4 + 7 = n(11)

arrayIsEqual (numArray, n) should return true, since 4 + 7 = n(11)

我如何使它工作?

我不希望它是2个随机数，而只是任意2个不同的数字加起来为n

I don't want it to be 2 random numbers, just any 2 different numbers that add up to n

推荐答案

您似乎正在尝试查看数组中是否有 any 两个数字加起来等于指定的值x.但是，您的代码只是随机选择两个数字，然后检查这些数字是否加起来.

It looks like you're trying to see if there are any two numbers in the array that add up to the specified value x. However, your code just picks two numbers at random and checks if those numbers add up.

Ruby具有 Array#combination 方法，该方法可以生成所有给定长度的组合:

Ruby has the Array#combination method, which generates all combinations of a given length:

def contains_pair_for_sum?(arr, n)
  !!arr.uniq.combination(2).detect { |a, b| a + b == n }
end

一些注意事项:

• 首先，我们根据Ruby约定对其进行命名:每个单词均为separated_by_underscores.最后的?表示该方法是谓词方法，并返回true或false值.

• First, we named it according to Ruby conventions: each word is separated_by_underscores. The ? on the end means that the method is a predicate method and returns a true or false value.

在该方法内部，发生了一些事情.让我们一步一步地看那条线.

Inside the method, a few things happen. Let's look at that line, piece by piece.

• arr:我们采用传入的数组.

• arr: We take the array that was passed in.

<...>.uniq:我们仅查看唯一元素(因为OP希望选择两个不同的数字).

<...>.uniq: We only look at the unique elements (because the OP wants to pick two different numbers).

<...>.combination(2):我们要求长度为2的数组的所有组合.如果数组为[4, 5, 6]，我们将得到[[4, 5], [4, 6], [5, 6]].

<...>.combination(2): We ask for all combinations from the array of length 2. If the array was [4, 5, 6], we'd get [[4, 5], [4, 6], [5, 6]].

<...>.detect { |a, b| a + b == n }:我们寻找第一个组合起来等于n的组合.如果找到一个，那就是该方法的结果.否则，我们得到nil.

<...>.detect { |a, b| a + b == n }: We look for the first combination that adds up to n. If we found one, that's the result of that method. Otherwise, we get nil.

!!<...>:最后，我们获取从detect获得的结果并将其取反两次.第一个否定产生一个布尔值(如果我们得到的值是nil，则为true；如果其他值为false，则为false)；第二个否定产生一个布尔值，该布尔值与第一个否定的真值相同.这是Ruby惯用语，用于将结果强制为true或false.

!!<...>: Finally, we take the result we got from detect and negate it twice. The first negation produces a Boolean value (true if the value we got was nil, or false if it's anything else); the second negation produces a Boolean value that's identical to the truth value of the first negation. This is a Ruby idiom to coerce a result into being either true or false.

让我们看看它的作用:

array = [4, 5, 9, 7, 8]

contains_pair_for_sum?(array, 11)
# => true (because [4, 7] sums to 11)

contains_pair_for_sum?(array, 17)
# => true (because [9, 8] sums to 17)

contains_pair_for_sum?(array, 100)
# => false (no pair matched)

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