Algorithm for finding characters in the same positions in a list of strings?

Question

Suppose I have:

1. Toby
2. Tiny
3. Tory
4. Tily

Is there an algorithm that can easily create a list of common characters in the same positions in all these strings? (in this case the common characters are 'T' at position 0 and 'y' at position 3)

I tried looking at some of the algorithms used for DNA sequence matching but it seems most of them are just used for finding common substrings regardless of their positions.

Answer 1

Finding a list of characters that are common in ALL strings at a certain position is trivially simple. Just iterate on each string for each character position 1 character position at a time. If any string's character is not the match of it's closest neighbor string's character, then the position does not contain a common character.

For any i = 0 to length -1... Once you find Si[x] != Si+1[x] you can skip to the next position x+1.

Where Si is the ith string in the list. And [x] is the character at position x.

Answer 2

Some generic code that has pretty poor performance O(n^2)

str[] = { "Toby", "Tiny", "Tory", "Tily" };
result = null;
largestString = str.getLargestString(); // Made up function
str.remove(largestString)
for (i = 0; i < largestString.length; i++) {
   hits = 0;
   foreach (str as value) {
      if (i < value.length) {
         if (value.charAt(i) == largestString.charAt(i))
            hits++;
      }
   }
   if (hits == str.length)
      result += largestString.charAt(i);
}
print(str.items);