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3463. Check If Digits Are Equal in String After Operations II

Description

You are given a string s consisting of digits. Perform the following operation repeatedly until the string has exactly two digits:

  • For each pair of consecutive digits in s, starting from the first digit, calculate a new digit as the sum of the two digits modulo 10.
  • Replace s with the sequence of newly calculated digits, maintaining the order in which they are computed.

Return true if the final two digits in s are the same; otherwise, return false.

 

Example 1:

Input: s = "3902"

Output: true

Explanation:

  • Initially, s = "3902"
  • First operation:
    • (s[0] + s[1]) % 10 = (3 + 9) % 10 = 2
    • (s[1] + s[2]) % 10 = (9 + 0) % 10 = 9
    • (s[2] + s[3]) % 10 = (0 + 2) % 10 = 2
    • s becomes "292"
  • Second operation:
    • (s[0] + s[1]) % 10 = (2 + 9) % 10 = 1
    • (s[1] + s[2]) % 10 = (9 + 2) % 10 = 1
    • s becomes "11"
  • Since the digits in "11" are the same, the output is true.

Example 2:

Input: s = "34789"

Output: false

Explanation:

  • Initially, s = "34789".
  • After the first operation, s = "7157".
  • After the second operation, s = "862".
  • After the third operation, s = "48".
  • Since '4' != '8', the output is false.

 

Constraints:

  • 3 <= s.length <= 105
  • s consists of only digits.

Solutions

Solution 1

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