hack.sol

pragma solidity ^0.8.9;

contract Hacks {
    bytes32 public constant hash =
        0x564ccaf7594d66b1eaaea24fe01f0585bf52ee70852af4eac0cc4b04711cd0e2;

    constructor() payable {}

    function solve(string memory solution) public {
        require(
            hash == keccak256(abi.encodePacked(solution)),
            "Incorrect answer"
        );

        (bool sent, ) = msg.sender.call{value: 10 ether}("");
        require(sent, "Failed to send Ether");
    }

    mapping(address => uint) public balances;

    function deposit() public payable {
        balances[msg.sender] += msg.value;
    }

    function withdraw() public {
        uint bal = balances[msg.sender];
        require(bal > 0);

        (bool sent, ) = msg.sender.call{value: bal}("");
        require(sent, "Failed to send Ether");

        balances[msg.sender] = 0;
    }
}