Converting A1 to R1C1 format - c

Question

As a follow up to my last question here.
I was trying out the reverse of the previous question. That is, converting an input of the form A1 to output of the form R1C1 (for more, look at my last question).
I'll explain my algorithm. Let us suppose we need to convert BC23 to R23C55. I extracted 'BC' and '23' from BC23 and stored them in seperate arrays. I made another array which stores values 1,2,3...so on for A,B,C respectively as and when they come in input. For example my array would contain 2 and 3 as first two elements respectively for B and C. Then I used some mathematics to convert it into a number, in this case 55 for BC.
Here is the complete code.
#include <stdio.h>
#include <string.h>
#include <math.h>
int main()
{
char str[5],col[5],row[5];
int i=0,j=0,k=0,lenOfstr,lenOfcol;
scanf("%s",str);
while(str[i]>='A'&&str[i]<='Z')
{
col[j]=str[i];
i++;
j++;
}
col[j]='\0';
lenOfstr=strlen(str);
lenOfcol=strlen(col);
int ascCol[lenOfcol];
for(i=lenOfcol;i<lenOfstr;i++)
{
row[k]=str[i];
k++;
}
row[k]='\0';
for(i=0;i<lenOfcol;i++)
{
ascCol[i]=col[i]-64;
}
int sum=0;
for(i=0;i<lenOfcol;i++)
{
sum=sum+(ascCol[i]*pow(26,lenOfcol-i-1));
}
printf("%d",sum);
return 0;
}
There is a slight bug in the last strip of code which I am not able to debug.
int sum=0;
for(i=0;i<lenOfcol;i++)
{
sum=sum+(ascCol[i]*pow(26,lenOfcol-i-1));
}
printf("%d",sum);
Input Z should give me output 26, and AA should give 27. But my code gives 26 on both. Thereafter output is always 1 less than what should be the correct output; BC gives 54 instead of 55.
Someone help me out.

Answer 1

Try changing the summation to this:
sum = sum * 26 + ascCol[i]
This avoids having to worry about unexpected floating point rounding behaviour and other issues caused by the fact that pow returns a floating point number.
Note you can simply your entire program to just this:
#include <stdio.h>
int main()
{
char str[5];
scanf("%s", str);
int i = 0;
int sum = 0;
while(str[i] >= 'A' && str[i] <= 'Z')
{
sum = sum * 26 + (str[i] - 'A');
i++;
}
printf("%d", sum);
return 0;
}