Find Excel Column Name From Column Number [ Microsoft, Amazon, Samsung ]

Problem:Given a positive integer, return its corresponding column title as appear in an Excel sheet.
MS Excel columns has a pattern like A, B, C, … ,Z, AA, AB, AC,…. ,AZ, BA, BB, … ZZ, AAA, AAB ….. etc.
In other words, column 1 is named as “A”, column 2 as “B”, column 27 as “AA”.

Link

#include <stdio.h>
#include <string.h>
#include <string>
#include <iostream>
using namespace std;
int main() {
	//code
	int t,i;
	char c;
	string p,prev;
	long long n,a;
	scanf("%d",&t);
	while(t--)
	{
	    scanf("%lld",&n);
	    p="";
	    prev="";
	    a=n;
	    while(a)
	    {
	        i=a%26;
	        a/=26;
	        if(i)
	        c=char(i+64);
	        else
	        {
	            c='Z';
	            a-=1;
	        }
	        p=c;
	        p.append(prev);
	        prev=p;
	    }
	    cout<<p<<"\n";
	}
	return 0;
}