golang - how to list excel column names ??

As shown in image , the exel columns are listed as A B C ... AA AB AC .... There is no sample available on how to list this in go lang. This is needed when parsing excel spreadsheet to get range of spreadsheet tabs to get cells values

CodePudding user response：

I tried to search for handy function to get excel column names but was not able to get in golang , so created one , hope this helps other to save time

package main

import "fmt"

func reverse(s string) string {
    runes := []rune(s)
    for i, j := 0, len(runes)-1; i < j; i, j = i 1, j-1 {
        runes[i], runes[j] = runes[j], runes[i]
    }
    return string(runes)
}

// Function to print Excel column
// name for a given column number
//
func getColumnName(columnNumber int) string {

    // To store result (Excel column name)
    var columnName = ""
    for ok := true; ok; ok = columnNumber > 0 {

        // Find remainder
        rem := columnNumber % 26

        // If remainder is 0, then a
        // 'Z' must be there in output
        if rem == 0 {
            columnName  = "Z"
            columnNumber = (columnNumber / 26) - 1
        } else // If remainder is non-zero
        {
            columnName  = string((rem - 1)   int('A'))
            columnNumber = columnNumber / 26
        }
    }

    // Reverse the string
    columnName = reverse(columnName)
    return columnName

}

func main() {
    for cm := 1; cm < 100; cm   {
        fmt.Println(getColumnName(cm))
    }
}

CodePudding user response：

Here is an efficient solution.

func getColumnName(col int) string {
    name := make([]byte, 0, 3) // max 16,384 columns (2022)
    const aLen = 'Z' - 'A'   1 // alphabet length
    for ; col > 0; col /= aLen   1 {
        name = append(name, byte('A' (col-1)%aLen))
    }
    for i, j := 0, len(name)-1; i < j; i, j = i 1, j-1 {
        name[i], name[j] = name[j], name[i]
    }
    return string(name)
}

https://go.dev/play/p/upjBQeE1x8I

The OP (@mahbh2001) posted an answer to his own question: https://stackoverflow.com/a/71350368

Here are the results of getColumnName benchmarks for columns 1 through 99:

rocka2q:
BenchmarkA2Q-4  758865  1498 ns/op   146 B/op   73 allocs/op

OP (mahbh2001):
BenchmarkOP-4   122714  9515 ns/op  1376 B/op  341 allocs/op

The OP's code is significantly slower.