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Ballot.sol

pragma solidity ^0.4.22;

contract Ballot {
    
    struct Voter {
        uint weight;
        bool voted;
        address delegate;
        uint vote;
    }
        
    address private chairperson;
    
    struct Proposal {
        bytes32 name;
        uint voteCount;
    }
    
    mapping (address => Voter) private voters;
    Proposal[] private proposals;
    
    modifier checkOwner {
        require(
            msg.sender == chairperson, 
            "Only chairperson can give right to vote."
        );
        _;
    }
    
    constructor(bytes32[] proposalNames) public {
        chairperson = msg.sender;
        voters[chairperson].weight = 1;
        
        for (uint i = 0; i < proposalNames.length; i++) {
            proposals.push(Proposal({
                name: proposalNames[i],
                voteCount: 0
            }));
        }
    }
    
    function giveRightToVote(address voter) checkOwner public {
        require(
            !voters[voter].voted,
            "Voter has already voted"
            );
            
        require(voters[voter].weight == 0);
        voters[voter].weight = 1;
    }
    
    function delegateVote(address to) public {
        Voter storage sender = voters[msg.sender];
        require(!sender.voted, "Sender has already voted");
        
        require(to != msg.sender, "Self delegate not allowed");
        
        while(voters[to].delegate != address(0)) {
            to = voters[to].delegate;
            require(to != msg.sender, "Loop not allowed");
        }
        sender.voted = true;
        sender.delegate = to;
        
        if (voters[to].voted) {
            proposals[voters[to].vote].voteCount += sender.weight;
        }
        else {
            voters[to].weight += sender.weight;
        }
    }
    
    function Vote(uint proposal) public {
        Voter storage sender = voters[msg.sender];
        require(!sender.voted, "Sender has already voted");
        sender.voted = true;
        sender.vote = proposal;
        
        proposals[proposal].voteCount += sender.weight;
    }
    
    function winningProposal() public view 
                returns (uint winningProposal_) {
        uint winnerCount = 0;
        for(uint i = 0; i < proposals.length; i++) {
            if (proposals[i].voteCount > winnerCount) {
                winnerCount = proposals[i].voteCount;
                winningProposal_ = i;
            }
        }
    }
    
    function winnerName() public view 
            returns (bytes32 winnerName_) {
        winnerName_ = proposals[winningProposal()].name;     
    }
    
}