2434. Using a Robot to Print the Lexicographically Smallest String

You are given a string s and a robot that currently holds an empty string t. Apply one of the following operations until s and t are both empty: - Remove the first character of a string s and give it to the robot. The robot will append this character to the string t. - Remove the last character of a string t and give it to the robot. The robot will write this character on paper. Return the lexi