colname.cpp

/*
Given a positive integer, return its corresponding column title as appear in an Excel sheet.
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” and so on.

Example 1:

Input:
N = 28
Output: AB
Explanation: 1 to 26 are A to Z.
Then, 27 is AA and 28 = AB.

Example 2:

Input: 
N = 13
Output: M
Explanation: M is the 13th character of
alphabet.
Your Task:
You don't need to read input or print anything. Your task is to complete the function colName()
 which takes the column number N as input and returns the column name represented as a string.
Expected Time Complexity: O(LogN).
Expected Auxiliary Space: O(1).

Constraints:
1 <= N <= 1018*/
#include<bits/stdc++.h>
using namespace std;
 string colName (long long int n)
    {
      if(n<=26)
      {
          string sd="";
          sd=sd+char(64+n);
          return sd;
      }
      string ans="";
      int t;
      while(n>0)
      {
         n--;
         t=n%26;
         ans=ans+char(65+(t));
         n=n/26;
      }
      reverse(ans.begin(),ans.end());
      cout<<ans;
      return ans;
    }
 int main()
 {
   int n;
   cout<<"\n enter the number:";
   cin>>n;
   colName(n);	
 }