I end up with 1 test failed, want you to review this.
results:
Actual: false
Expected: true
Number: 11247699674211
Completed in 0.6927ms
Log
num index = 8
expected digit = 6
sum of prev digits = 3
sum of digit squared = 9

Why it should be true?

Practically the same as this kata.

• No random tests
• Duplicate

• It's "absolute difference", and not "absolute subtract"
• The existence of string length limitation doesn't make any sense, and the strings of such length are not even tested
• The initial solution includes useless code
• Char arrays is not a "modern C++" way
• No random tests
• Summing an array of numbers is not a novel idea