Problem

You are given three strings: s1, s2, and s3. In one operation you can choose one of these strings and delete its rightmost character. Note that you cannot completely empty a string.

Return the minimum number of operations required to make the strings equal. If it is impossible to make them equal, return -1.

Example 1:

Input: s1 = “abc”, s2 = “abb”, s3 = “ab”

Output: 2

Explanation: Deleting the rightmost character from both s1 and s2 will result in three equal strings.

Example 2:

Input: s1 = “dac”, s2 = “bac”, s3 = “cac”

Output: -1

Explanation: Since the first letters of s1 and s2 differ, they cannot be made equal.

Constraints:

1 <= s1.length, s2.length, s3.length <= 100 s1, s2 and s3 consist only of lowercase English letters.

Pre analysis

The idea is to find the first common character from all string and then count the length of the string from that character. If there is no common character, then return -1.