Check If Digits Are Equal in String After Operations II

• Start a loop that continues as long as the length of the string s is greater than 2.
• Inside the loop, create a new StringBuilder to build the string for the next iteration.
• Iterate through the current string s from the first character up to the second-to-last character.
• For each index i, parse the digits at s[i] and s[i+1], calculate their sum modulo 10.
• Append the resulting digit to the StringBuilder.
• After the inner loop, replace s with the string generated by the StringBuilder.
• Once the loop terminates (when s has a length of 2), compare the two characters of s.
• Return true if they are equal, and false otherwise.

The most straightforward way to solve the problem is to follow the instructions literally. We can use a loop that continues as long as the string's length is more than 2. In each iteration of the loop, we construct the next version of the string by iterating through the current one, taking consecutive pairs of digits, summing them up modulo 10, and appending the result to a new string builder. Once the new string is fully constructed, we replace the old string with it. This process is repeated until the string length is reduced to 2. Finally, we compare the two digits of the resulting string.

1class Solution {2    public boolean checkEqual(String s) {3        while (s.length() > 2) {4            StringBuilder next_s = new StringBuilder();5            for (int i = 0; i < s.length() - 1; i++) {6                int digit1 = s.charAt(i) - '0';7                int digit2 = s.charAt(i + 1) - '0';8                int sum = (digit1 + digit2) % 10;9                next_s.append(sum);10            }11            s = next_s.toString();12        }13        return s.charAt(0) == s.charAt(1);14    }15}