2_VoteTwoChoices.sol

/* This program is free software. It comes without any warranty, to
the extent permitted by applicable law. You can redistribute it
and/or modify it under the terms of the Do What The Fuck You Want
To Public License, Version 2, as published by Sam Hocevar. See
http://www.wtfpl.net/ for more details. */

/* These contracts are examples of contracts with vulnerabilities in order to practice your hacking skills.
DO NOT USE THEM OR GET INSPIRATION FROM THEM TO MAKE CODE USED IN PRODUCTION */

pragma solidity ^0.4.10;

// You can buy voting rights by sending ether to the contract.
// You can vote for the value of your choice.
contract VoteTwoChoices{
    mapping(address => uint) public votingRights;
    mapping(address => uint) public votesCast;
    mapping(bytes32 => uint) public votesReceived;

    /// @dev Get 1 voting right per ETH sent.
    function buyVotingRights() payable {
        votingRights[msg.sender]+=msg.value/(1 ether);
    }

    /** @dev Vote with nbVotes for a proposition.
     *  @param _nbVotes The number of votes to cast.
     *  @param _proposition The proposition to vote for.
     */
    function vote(uint _nbVotes, bytes32 _proposition) {
        require(_nbVotes + votesCast[msg.sender]<=votingRights[msg.sender]); // Check you have enough voting rights.

        votesCast[msg.sender]+=_nbVotes;
        votesReceived[_proposition]+=_nbVotes;
    }

}