CODEWITHSUNDEEP
javascript
Angshu31
Angshu31

Reputation: 1270

Change number to corresponding letters

My question is how do I get the corresponding letter(s) from a number.

So

0    =>   0    // 0 stays 0
1    =>   A
2    =>   B
3    =>   C
26   =>   Z
27   =>   AA
28   =>   AB
55   =>   AC
702  =>   ZZ

The number will definitely not be over 702.

Is there some kind of method I can use to do this?

Upvotes: 1

Views: 193

Answers (3)

FZs
FZs

Reputation: 18619

Split the number into parts by doing a modulo by 26, then use String.fromCharCode to convert it to a character:

function numToExcelColumnName(n){
  if(!n) return 0

  n-- //Make 0 => A

  const lower = n % 26
  const upper = Math.floor(n / 26)
  
  return (
    upper 
      ? String.fromCharCode(65 + upper - 1) 
      : ''
  ) 
  + String.fromCharCode(65 + lower)
}

You can even extend this code to handle numbers above 702 as well by adding a loop:

function numToExcelColumnName(n){ 
  if(!n) return 0
    
  let output = ''
  while(n){
    n--
    output = String.fromCharCode(65 + n % 26) + output
    n = Math.floor(n / 26)
  }
  return output
}

Upvotes: 2

iAmOren
iAmOren

Reputation: 2804

I liked the challenge, so I wrote the following code:

function NumbersToLetters(num) {
  var letArr=[];
  function numToLet(letterArray, number) {
    if(number>0) {
      var whole=Math.floor((number-1)/26);
      var reminder=(number-1)%26;
      letterArray.unshift(String.fromCharCode(65+reminder));
        numToLet(letterArray, whole);
    }
  };
  numToLetters(letArr, num);
  return letArr.length?letArr.join(""):"0";
}

To be used:

NumbersToLetters(num);

Upvotes: 0

user13715010
user13715010

Reputation:

For single characters like A,B... you can get the number easily by

num = ord(x)-65 where x is the corresponding character (A,B...)

For Double letters like (AB,BG,..)

num = ord(str[0]-65)*26+(str[1]-65) where str = xy where x and y are corresponding characters

Upvotes: 0

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