Leetcode 1585. Check If String Is Transformable With Substring Sort Operations

Given two equal-length digit strings s and t, determine whether s can be transformed into t by repeatedly choosing substrings and sorting them in ascending order in-place. The core challenge is to check whether each digit required by t can be moved into position from s without being blocked by smaller digits, i.e., whether the relative order constraints imposed by substring-sorts allow the target arrangement.