Examples :
Input: arr [] = {“abc”, “abd”, “bbd”}
Output: 2
(abc, abd) and (abd, bbd) are the only valid pairs.Input: arr [] = {“Def”, “deg”, “dmf”, “xef”, “dxg”}
Output: 4
Method 1: For each possible pair, check if both strings differ at exactly the same index position with one row traversal.
Method 2: two strings can be compare as follows to check if they differ at the same index position:
Let str1 = “abc” and str2 = “adc”
For str1 , add “#bc” , “a # c” and “ab #” to a set .
Now for str2 , generate the string in the similar manner and if any of the generated string
is already present in the set then both the strings differ in exactly 1 index position.
For example, “a # c” is one of the generated strings.
Note that “#” is used because it will not be a part of any of the original strings.
Below is the implementation of the above approach:

Exit :
2