freeCodeCamp/curriculum/challenges/chinese/22-rosetta-code/rosetta-code-challenges/babbage-problem.md

id, title, challengeType, forumTopicId, dashedName

id	title	challengeType	forumTopicId	dashedName
594db4d0dedb4c06a2a4cefd	巴贝奇问题	1	302229	babbage-problem

--description--

Charles Babbage, looking ahead to the sorts of problems his Analytical Engine would be able to solve, gave this example:

What is the smallest positive integer whose square ends in the digits 269,696? 巴贝奇，给鲍登勋爵的信，1837 年；参见 Hollingdale and Tootill, Electronic Computers, second edition, 1970, p. 125。

他认为答案可能是 99,736，其平方是 9,947,269,696；但他不能确定。

任务是找出巴贝奇是否有正确的答案。

--instructions--

实现一个函数来返回满足 Babbage 问题的最小整数。 如果巴贝奇是对的，返回巴贝奇的数字。

--hints--

babbage 应该是一个函数。

assert(typeof babbage === 'function');

babbage(99736, 269696) 不应返回 99736（有一个较小的答案）。

assert.equal(babbage(babbageAns, endDigits), answer);

--seed--

--after-user-code--

const babbageAns = 99736;
const endDigits = 269696;
const answer = 25264;

--seed-contents--

function babbage(babbageNum, endDigits) {

  return true;
}

--solutions--

function babbage(babbageAns, endDigits) {
  const babbageNum = Math.pow(babbageAns, 2);
  const babbageStartDigits = parseInt(babbageNum.toString().replace('269696', ''));
  let answer = 99736;

  // count down from this answer and save any sqrt int result. return lowest one
  for (let i = babbageStartDigits; i >= 0; i--) {
    const num = parseInt(i.toString().concat('269696'));
    const result = Math.sqrt(num);
    if (result === Math.floor(Math.sqrt(num))) {
      answer = result;
    }
  }

  return answer;
}