Excel Sheet Column Number

Description

Given a column title as appear in an Excel sheet, return its corresponding column number.

For example:

A -> 1
B -> 2
C -> 3
...
Z -> 26
AA -> 27
AB -> 28 

Given a positive integer, return its corresponding column title as appear in an Excel sheet.

For example:

1 -> A
2 -> B
3 -> C
...
26 -> Z
27 -> AA
28 -> AB 

Hint

Train of Thought

Code

//titile to number
public int titleToNumber(String s) {
    int result = 0;
    for(int i = 0 ; i < s.length(); i++) {
      result = result * 26 + (s.charAt(i) - 'A' + 1);
    }
    return result;
  }

  //number to chars
  public class Solution {
    public String convertToTitle(int n) {
        StringBuilder result = new StringBuilder();

        while(n>0){
            n--;
            result.insert(0, (char)('A' + n % 26));
            n /= 26;
        }

        return result.toString();
    }
}

Complexity