求和大整数 [英] Sum Big Integers

问题描述

我目前正陷在Codewars挑战中，我无法理解:

I'm currently stuck on a Codewars challenge that I can't get my head around:

给出两个整数的字符串表示形式，返回这些整数的字符串表示形式，例如sumStrings('1','2') // => '3'

Given a string representation of two integers, return the string representation of those integers, e.g. sumStrings('1','2') // => '3'

到目前为止，我已使用以下代码，但由于将数字转换为科学计数法，因此在大量测试用例中均失败:

I've used the following code so far, but it fails on large number test cases as the number is converted into a scientific notation:

function sumStrings(a,b) {
  var res = +a + +b;
  return res.toString();
}

任何帮助将不胜感激.

小提琴示例: https://jsfiddle.net/ag1z4x7d/

推荐答案

问题是在特定的kata(IIRC)中，对于常规的32位整数，存储在a和b中的数字太大，和浮点运算是不精确的.因此，您的版本没有返回正确的值:

The problem is that in that specific kata (IIRC), the numbers stored in a and b are too large for a regular 32 bit integer, and floating point arithmetic isn't exact. Therefore, your version does not return the correct value:

sumStrings('100000000000000000000', '1')
// returns '100000000000000000000' instead of '100000000000000000001'

您必须确保不会发生这种情况.一种方法是进行良好的老式基于进位的加法，并在整个计算过程中始终停留在基于数字/字符的世界中:

You have to make sure that this does not happen. One way is to do an good old-fashioned carry-based addition and stay in the digit/character based world throughout the whole computation:

function sumStrings(a, b) {
   var digits_a = a.split('')
   var digits_b = b.split('')
   ...
}

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