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LeetCode 阶乘后的零算法题解 All In One

factorial

阶乘后的零原理 图解

1. 实现 factorial
2. 计算后面 0 的个数，除 0! 本身的 0

阶乘!

https://www.shuxuele.com/numbers/factorial.html
https://www.shuxuele.com/definitions/factorial.html

172. 阶乘后的零

172. Factorial Trailing Zeroes

function trailingZeroes(n: number): number {
  if(n === 0) return 0;
  function factorial(n, multi = 1) {
    if(n === 1) return multi;
    multi *= n;
    return factorial(n - 1, multi)
  }
  const num = factorial(n);
  const arr:string[] = `${num}`.split(``).reverse();
  let len: number = 0;
  for(const item of arr) {
    if(item === '0') {
      len += 1;
    } else {
      break;
    }
  }
  return len;
};

// 大数相乘 ???

// testCase factorial(30) = 2.652528598121911e+32 ❌
// 通过测试用例：21 / 500
// 输入：30 输出：0 预期结果：7

/* 

(() => {
  const log = console.log;
  function factorial(n, multi = 1) {
    if(n === 0) {
      return 0;
    }
    if(n === 1) {
      return multi;
    }
    multi = n * multi;
    return factorial(n - 1, multi);
  };

  const arr = [...new Uint8Array(100)].map((item, i) => i);
  // for (const [item, i] of arr.entries()) {
  //   log(`item, i =`, item, i);
  // }
  for (const item of arr) {
    log(`testCase factorial(${item}) =`, factorial(item));
    if(`${factorial(item)}`.includes(`e`)) {
      break;
    }
  }
  // factorial(50)
  // 3.0414093201713376e+64
  // 阶乘, `科学计数法` `e` bug ❌
})();

*/


/*

$ npx ts-node ./172\ factorial-trailing-zeroes.ts

testCase factorial(0) = 0
testCase factorial(1) = 1
testCase factorial(2) = 2
testCase factorial(3) = 6
testCase factorial(4) = 24
testCase factorial(5) = 120
testCase factorial(6) = 720
testCase factorial(7) = 5040
testCase factorial(8) = 40320
testCase factorial(9) = 362880
testCase factorial(10) = 3628800
testCase factorial(11) = 39916800
testCase factorial(12) = 479001600
testCase factorial(13) = 6227020800
testCase factorial(14) = 87178291200
testCase factorial(15) = 1307674368000
testCase factorial(16) = 20922789888000
testCase factorial(17) = 355687428096000
testCase factorial(18) = 6402373705728000
testCase factorial(19) = 121645100408832000
testCase factorial(20) = 2432902008176640000
testCase factorial(21) = 51090942171709440000
testCase factorial(22) = 1.1240007277776077e+21

*/

LeetCode 题解 / LeetCode Solutions

https://www.youtube.com/channel/UCftIXZeipv4MTVwmfFphtYw/videos

YouTube & LeetCode 力扣官方算法题解视频列表

https://www.youtube.com/playlist?list=PLamwFu9yMruCBtS2tHUD77oI_Wsce-syE

https://github.com/xgqfrms/leetcode/issues/14

https://www.youtube.com/results?search_query=+Leetcode+172

<iframe allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen="" frameborder="0" height="315" src="https://www.youtube.com/embed/3Hdmv_Ym8PI?start=40" title="YouTube video player" width="560"></iframe>

https://neetcode.io/

~~

https://github.com/neetcode-gh/leetcode/blob/main/javascript/172-Factorial-Trailing-Zeroes.js

https://github.com/neetcode-gh/leetcode/blob/main/typescript/172-Factorial-Trailing-Zeroes.ts

~~

类似问题

LeetCode

https://leetcode.com/problems//

refs

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标签：multi,factorial,题解,testCase,item,https,阶乘,com,LeetCode
From： https://www.cnblogs.com/xgqfrms/p/16767496.html