JavaScript 進位制轉換 All In One

xgqfrms發表於2024-05-28
JavaScript

JavaScript 進位制轉換 All In One

js base conversion

image

native solutions

  1. 十進位制轉二進位制

Number.prototype.toString() 將十進位制數子轉換為 二進位制、八進位制、十六進制 等進位制的字串

(5).toString(2);
// '101'

let tTob = (5).toString(2);
console.log(tTob, typeof tTob);
// 101 string


(5).toString(2);
// '101'
(5.5).toString(2);
// '101.1'
(5.6).toString(2);
// '101.1001100110011001100110011001100110011001100110011'

radix 基數

radix Optional
An integer in the range 2 through 36 specifying the base to use for representing the number value.
Defaults to 10.

toString()
toString(radix)

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toString

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/toString

  1. 二進位制轉十進位制
parseInt('101', 2);
// 5

let bTot = parseInt('101', 2);
console.log(bTot, typeof bTot);
// 5 'number'

radix 基數

radix Optional
An integer between 2 and 36 that represents the radix (the base in mathematical numeral systems) of the string.
It is converted to a 32-bit integer;
if it's nonzero and outside the range of [2, 36] after conversion, the function will always return NaN.
If 0 or not provided, the radix will be inferred based on string's value.
Be careful — this does not always default to 10!
The description below explains in more detail what happens when radix is not provided.

parseInt(string)
parseInt(string, radix)

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseInt

pure js solutions

// js 演算法實現

demos


function countBits(n: number): number[] {
  let temp = [];
  for(let i = 0; i <= n; i ++) {
    // js 二進位制 轉換
    let b = [...tTob(i)].filter(i => i === `1`).length;
    temp.push(b); 
  }
  return temp;
};

function tTob (t: number): string {
  return t.toString(2);
}

https://leetcode.com/problems/counting-bits/description/?envType=study-plan-v2&envId=leetcode-75


// function tTob (t: number): string {
//   let i = 0;
//   let str = 0;
//   if(t % 2 !== 0) {
//     str += 1;
//   } else {
//     str += 0;
//   }
//   while(2**i < t) {
//     i += 1;
//     str += 10**i;
//     // if(i % 2 !== 0) {
//     //   str += 10**i;
//     // }
//   }
//   // while(t / 2) {
//   //   t = Math.floor(t / 2);
//   //   i += 1;
//   //   str += 10**i;
//   // }
//   console.log(`str =`, str);
//   return `${str}`;
// }

// function tTob (t: number): string {
//   let n = 0;
//   while(2**n < t) {
//     n += 1;
//   }
//   console.log(`n =`, n);
//   let str = 0;
//   if(t % 2 !== 0) {
//     str += 1;
//   } else {
//     str += 0;
//   }
//   let sum = str;
//   for(let i = 1; i <= n; i++) {
//     if(sum + 2**i < t) {
//       str += 10**i;
//       sum += 2**i;
//     }
//   }
//   console.log(`str =`, str);
//   return `${str}`;
// }


// function tTob (t: number): str {
//   let str = ``;
//   let n = 0;
//   while(2**n < t) {
//     n += 1;
//   }
//   console.log(`n =`, n);
//   let sum = 0;
//   for(let i = 0; i < n; i++) {
//     sum += 2**i;
//     if(sum < t) {
//       str += i 
//     }
//   }
//   return str;
//   // return parseInt(str, 10);
//   // return parseInt(t, 2);
// }

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JavaScript 進位制轉換

LeetCode 171. Excel Sheet Column Number / Excel 工作表列號

function titleToNumber(columnTitle: string): number {
  // 如何動態生成 字典 ✅ 26 進位制
  // A-Z -> 1-26
  const strs = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
  const obj = {};
  for(let i = 0; i < strs.length; i++) {
    obj[strs[i]] = i + 1;
  }
  let result = 0
  const arr = columnTitle.split('')
  let n = arr.length;
  for(let i = 0; i < n; i++) {
    let num = obj[arr[i]];
    result += num * 26 ** (n - i - 1);
  }
  return result
};


/* 

str = `A`
str.charAt(0)
// 65
str.charCodeAt(0)
// 65
str.codePointAt(0)
// 65

 */

https://leetcode.com/problems/excel-sheet-column-number/

https://www.cnblogs.com/xgqfrms/p/17650033.html

refs

https://www.cnblogs.com/jimojianghu/p/15624693.html

https://www.mlxz.top/index.php/archives/69/

https://stackoverflow.com/questions/1337419/how-do-you-convert-numbers-between-different-bases-in-javascript

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