将整数转换为等效的 alpha 有序列表

发布于 2024-12-04 21:59:34 字数 850 浏览 2 评论 0原文

我需要一个函数将整数转换为等效的 alpha 有序列表索引。例如：

1 = a
2 = b
.
.
.
26 = z
27 = AA
28 = ab
.
.
等等。

目前，我有以下几乎工作，但某处存在一个小逻辑错误，使其不太正确（它会斧头，哎，<强>bz，ba，bb，bc...）：

function intToAlpha( int ) {

    var asciiStart = 97,
        alphaMax = 26,
        asciiCode,
        char,
        alpha = '',
        place,
        num,
        i;

    for ( i = 0; Math.pow(alphaMax, i) < int; i++ ) {

        place = Math.pow(alphaMax, i);        
        num = Math.floor( ( int / place ) % alphaMax);
        asciiCode = ( num == 0 ? alphaMax : num ) + asciiStart - 1;
        char = String.fromCharCode(asciiCode);
        alpha = char + alpha;

    }

    return alpha;
}

for (i = 1; i < 300; i++) {
    console.log( i + ': ' + intToAlpha(i) );
}

原文

I need to a function to convert an integer to the equivalent alpha ordered list index. For example:

1 = a
2 = b
.
.
.
26 = z
27 = aa
28 = ab
.
.
etc.

Currently I have the following which almost works but there's a small logic error somewhere that makes it not quite get it right (it goes ax, ay, bz, ba, bb, bc...):

function intToAlpha( int ) {

    var asciiStart = 97,
        alphaMax = 26,
        asciiCode,
        char,
        alpha = '',
        place,
        num,
        i;

    for ( i = 0; Math.pow(alphaMax, i) < int; i++ ) {

        place = Math.pow(alphaMax, i);        
        num = Math.floor( ( int / place ) % alphaMax);
        asciiCode = ( num == 0 ? alphaMax : num ) + asciiStart - 1;
        char = String.fromCharCode(asciiCode);
        alpha = char + alpha;

    }

    return alpha;
}

for (i = 1; i < 300; i++) {
    console.log( i + ': ' + intToAlpha(i) );
}

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累赘 2024-12-11 21:59:34

该函数在 NVu/Kompozer/SeaMonkey Composer 中使用，稍加调整即可直接生成小写字母：

function ConvertArabicToLetters(num)
{
  var letters = "";
  while (num > 0) {
    num--;
    letters = String.fromCharCode(97 + (num % 26)) + letters;
    num = Math.floor(num / 26);
  }
  return letters;
}

This function is used in NVu/Kompozer/SeaMonkey Composer, with a small tweak to generate lower case directly:

function ConvertArabicToLetters(num)
{
  var letters = "";
  while (num > 0) {
    num--;
    letters = String.fromCharCode(97 + (num % 26)) + letters;
    num = Math.floor(num / 26);
  }
  return letters;
}

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眼中杀气 2024-12-11 21:59:34

您需要确保在获取 mod 时使用正确的值。

function intToAlpha( int ) {
var asciiStart = 97,
    alphaMax = 26,
    asciiCode,
    char,
    alpha = "";
    while(int > 0) {
        char = String.fromCharCode(asciiStart + ((int-1) % alphaMax));
        alpha = char + alpha;
        int = Math.floor((int-1)/26);
    }
    return alpha;
}

You need to make sure that you use the correct value when taking the mod.

function intToAlpha( int ) {
var asciiStart = 97,
    alphaMax = 26,
    asciiCode,
    char,
    alpha = "";
    while(int > 0) {
        char = String.fromCharCode(asciiStart + ((int-1) % alphaMax));
        alpha = char + alpha;
        int = Math.floor((int-1)/26);
    }
    return alpha;
}

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七秒鱼° 2024-12-11 21:59:34

不久前，我在 SQL 中需要同样的东西，所以我问（并回答）了这个问题多基转换 - 使用 URL 缩短器的所有组合。

让它变得复杂的是，它不是直接的基数转换，因为没有代表零数字的字符。

我将 SQL 函数转换为 Javascript：

function tinyEncode(id) {

  var code, value, adder;

  var chars = 'abcdefghijklmnopqrstuvwxyz';

  if (id <= chars.length) {
    code = chars.substr(id - 1, 1);
  } else {
    id--;
    value = chars.length;
    adder = 0;
    while (id >= value * (chars.length + 1) + adder) {
      adder += value;
      value *= chars.length;
    }
    code = chars.substr(Math.floor((id - adder) / value) - 1, 1);
    id = (id - adder) % value;
    while (value > 1) {
      value = Math.floor(value / chars.length);
      code += chars.substr(Math.floor(id / value), 1);
      id = id % value;
    }
  }
  return code;
}

演示： http://jsfiddle.net/Guffa/mstBe/

A while back I needed the same thing in SQL, so I asked (and answered) the question Multi-base conversion - using all combinations for URL shortener.

The thing that is making it complicated is that it's not a straight base conversion, as there is no character representing the zero digit.

I converted the SQL function into Javascript:

function tinyEncode(id) {

  var code, value, adder;

  var chars = 'abcdefghijklmnopqrstuvwxyz';

  if (id <= chars.length) {
    code = chars.substr(id - 1, 1);
  } else {
    id--;
    value = chars.length;
    adder = 0;
    while (id >= value * (chars.length + 1) + adder) {
      adder += value;
      value *= chars.length;
    }
    code = chars.substr(Math.floor((id - adder) / value) - 1, 1);
    id = (id - adder) % value;
    while (value > 1) {
      value = Math.floor(value / chars.length);
      code += chars.substr(Math.floor(id / value), 1);
      id = id % value;
    }
  }
  return code;
}

Demo: http://jsfiddle.net/Guffa/mstBe/

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