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ballot.sol

pragma solidity >=0.4.22 <0.6.0;
contract Ballot {

    struct Voter {
        uint weight;
        bool voted;
        uint8 vote;
        address delegate;
    }
    struct Proposal {
        uint voteCount;
    }

    address chairperson;
    mapping(address => Voter) voters;
    Proposal[] proposals;

    /// Create a new ballot with $(_numProposals) different proposals.
    constructor(uint8 _numProposals) public {
        chairperson = msg.sender;
        voters[chairperson].weight = 1;
        proposals.length = _numProposals;
    }

    /// Give $(toVoter) the right to vote on this ballot.
    /// May only be called by $(chairperson).
    function giveRightToVote(address toVoter) public {
        if (msg.sender != chairperson || voters[toVoter].voted) return;
        voters[toVoter].weight = 1;
    }

    /// Delegate your vote to the voter $(to).
    function delegate(address to) public {
        Voter storage sender = voters[msg.sender]; // assigns reference
        if (sender.voted) return;
        while (voters[to].delegate != address(0) && voters[to].delegate != msg.sender)
            to = voters[to].delegate;
        if (to == msg.sender) return;
        sender.voted = true;
        sender.delegate = to;
        Voter storage delegateTo = voters[to];
        if (delegateTo.voted)
            proposals[delegateTo.vote].voteCount += sender.weight;
        else
            delegateTo.weight += sender.weight;
    }

    /// Give a single vote to proposal $(toProposal).
    function vote(uint8 toProposal) public {
        Voter storage sender = voters[msg.sender];
        if (sender.voted || toProposal >= proposals.length) return;
        sender.voted = true;
        sender.vote = toProposal;
        proposals[toProposal].voteCount += sender.weight;
    }

    function winningProposal() public view returns (uint8 _winningProposal) {
        uint256 winningVoteCount = 0;
        for (uint8 prop = 0; prop < proposals.length; prop++)
            if (proposals[prop].voteCount > winningVoteCount) {
                winningVoteCount = proposals[prop].voteCount;
                _winningProposal = prop;
            }
    }
}

ballot_test.sol

import "remix_tests.sol"; // this import is automatically injected by Remix.
import "./ballot.sol";

contract test3 {
   
    Ballot ballotToTest;
    function beforeAll () public {
       ballotToTest = new Ballot(2);
    }
    
    function checkWinningProposal () public {
        ballotToTest.vote(1);
        Assert.equal(ballotToTest.winningProposal(), uint(1), "1 should be the winning proposal");
    }
    
    function checkWinninProposalWithReturnValue () public view returns (bool) {
        return ballotToTest.winningProposal() == 1;
    }
}

CashJoin.sol

pragma solidity ^0.4.16;

contract CashJoin{
    address master = msg.sender;
    address opponent = 0;
    bool _init = false;
    uint reward;
    
    bool _completed = false;
    
    function init() payable {
        require(_init == false);
        require(msg.value > 1 ether);
        reward = msg.value * 2;
        _init = true;
    }
    
    function join() payable {
        require(_init);
        require(opponent == 0);
        require(master != msg.sender);
        require(msg.value == reward/2);
        opponent = msg.sender;
    }
    
    function winMaster(){
        require(opponent != 0);
        require(_init);
        require(!_completed);
        master.transfer(reward);
        reward = 0;
        _completed = true;
    }
    
    function getStatus() public constant returns (address, address, uint) {
        require(_init);
        require(!_completed);
        require(opponent != 0);
        return (master, opponent, reward);
    }
}

Hello_World.sol

pragma solidity ^0.4.16;

contract HelloWorld {
    uint256 counter = 5;
    address owner = msg.sender; //set owner as msg.sender
    
    function add() public {
      counter++;
    }
    
    function subtract() public { //decreases counter by 1
      counter--;
    }
    
    function getCounter() public constant returns (uint256) {
        return counter;
    } 
    
    function kill() public 
    { 
        //self-destruct function, 
        if(msg.sender == owner)
            selfdestruct(owner); 
    }

    
    function () public payable {
 
    }
}

TickTackToor.sol

pragma solidity ^0.4.16;


/**
 * A Two Player TicTacToe Game played using a smart contract.
 * P.S. I am just starting to learn solidity.
 * Author: madhawav
 */

contract TicTacToe 
{
    uint boardWidth;
    uint[] cells;
    
    address master = msg.sender;
    address player1;
    address player2;
    uint nextTurn = 0;
 
    /**
     * Must be called by the initiator of contract. Starts a game between caller and a specified opponent
     */
    function init(uint size, address opponent) public{
        if(msg.sender == master && opponent != master)
        {
            boardWidth = size;
            cells = new uint[](size*size);
            player1 = master;
            player2 = opponent;
            nextTurn = 1;
        }
    }
    
    /**
     * Preview board
     */
    function getBoard() public constant returns (uint[]) {
        return cells;
    } 
    
    /**
     * View players in game
     */
    function getPlayers() public constant returns (address,address){
        return (player1, player2);   
    }
    
    
    function _setCell(uint x, uint y, uint val) internal {
        cells[y*boardWidth + x] = val;
    }
    
    /**
     * Returns true if my turn
     */
    function checkMyTurn() constant returns (bool){
        if(checkResult() != 0)
            return false;
        address turnAddress = player1;
        if(nextTurn == 2)
            turnAddress = player2;
            
        if(msg.sender == turnAddress)
            return true;
        return false;
    }
    
    function _passTurn() internal {
        if(nextTurn == 1)
            nextTurn = 2;
        else
            nextTurn = 1;
    }
    
    function _getCell(uint x, uint y) internal constant returns (uint){
        return cells[y*boardWidth + x];
    }
    
    /**
     * Play my turn
     */
    function playCell(uint x, uint y) public {
        if(checkMyTurn())
        {
            if(_getCell(x,y) == 0)
            {
                _setCell(x,y,nextTurn);
                _passTurn();
            }
        }
    }
    
    /**
     * Check game status
     * 0: Game on
     * 1: Player 1 has won
     * 2: Player 2 has won
     * 3: Game has tied
     * 4: Game has not started yet
     */
    function checkResult() constant returns (uint){
        if(nextTurn == 0)
            return 4; // Game has not started yet
        if(isWin(1))
            return 1;
        if(isWin(2))
            return 2;
        
        //Check for blank cells
        for(uint i = 0; i < boardWidth*boardWidth; i++)
        {
            if(cells[i] == 0)
                return 0;  // Game still on
        }
        return 3; //Draw
    }
    
    function isWin(uint player) internal constant returns (bool) {
        // Check rows
        for(uint y = 0; y < boardWidth; y++){
            bool failed = false;
            for(uint x = 0; x < boardWidth; x++){
                if(_getCell(x,y) != player)
                {
                    failed = true;
                    break;
                }
            }
            if(!failed)
                return true;
        }
        
        //Check columns
        for(x = 0; x < boardWidth; x++){
            failed = false;
            for(y = 0; y < boardWidth; y++){
                if(_getCell(x,y) != player)
                {
                    failed = true;
                    break;
                }
            }
            if(!failed)
                return true;
        }
        
        // Positive Diagonal
        failed = false;
        for(x = 0; x < boardWidth; x++)
        {
            if(_getCell(x,x) != player)
            {
                failed = true;
                break;
            }
        }
        if(!failed)
            return true;
            
        // Negative Diagonal
        failed = false;
        for(x = 0; x < boardWidth; x++)
        {
            if(_getCell(boardWidth - x - 1,x) != player)
            {
                failed = true;
                break;
            }
        }
        if(!failed)
            return true;
        
    }
 
}

TicTacToeCash.sol

pragma solidity ^0.4.16;

/**
 * Two player TicTacToe Game played using Smart Contracts.
 * The player 1 deploys the smart contract and calls init, specifying the board size. The init transaction should carry atleast 1 ether. The winner's reward will be 2 * init amount. 
 * The player 2 joins the game. The transaction value should match init transaction value.
 * Player 2 makes the first move using playCell call. 
 * Players make moves in turns.
 * Winner receives the reward.
 * A player can check whether its their move using getStatus call. 
 * getBoard call can be used to preview game board.
 * getStatus call can be used to get stage (preinit, prejoin, started, player1Won, player2Won, drawn), players' addresses and winner's reward. 
 * 
 * Author: madhawav
 */

contract TicTacToeCash {
    address master = msg.sender;
    address player1 = 0;
    address player2 = 0;
    uint nextTurn = 0;
    uint boardWidth;
    uint[] cells;
    Stages stage = Stages.preinit;
    uint reward;
    
    enum Stages{
     preinit, prejoin, started, player1Won, player2Won, drawn   
    }

    /**
     * Start game as player 1
     */
    function init(uint size) payable {
        require(stage == Stages.preinit);
        require(master == msg.sender);
        require(size >= 2);
        require(msg.value >= 1 ether);
        reward = msg.value * 2;
        player1 = msg.sender;
        
        boardWidth = size;
        cells = new uint[](size*size);
        stage = Stages.prejoin;
    }
    
    /**
     * Preview board.
     */
    function getBoard() public constant returns (uint[]) {
        require(stage == Stages.started || stage == Stages.player1Won || stage == Stages.player2Won || stage == Stages.drawn);
        require(msg.sender == player1 || msg.sender == player2);
        return cells;
    } 
    
    /**
     * Join as player 2
     */
    function join() payable {
        require(stage == Stages.prejoin);
        require(player2 == 0);
        require(player1 != msg.sender);
        require(msg.value == reward/2);
        player2 = msg.sender;
        nextTurn = 2;
        stage = Stages.started;
    }
    
        
    function _getCell(uint x, uint y) internal constant returns (uint){
        return cells[y*boardWidth + x];
    }
    
    function _setCell(uint x, uint y, uint val) internal {
        cells[y*boardWidth + x] = val;
    }
    
    
    /**
     * Returns true if my turn
     */
    function checkMyTurn() constant returns (bool){
        require(stage==Stages.started);
        require(msg.sender == player1 || msg.sender == player2);
        address turnAddress = player1;
        if(nextTurn == 2)
            turnAddress = player2;
            
        if(msg.sender == turnAddress)
            return true;
        return false;
    }
    
    function _passTurn() internal {
        if(nextTurn == 1)
            nextTurn = 2;
        else
            nextTurn = 1;
    }
    
    /**
     * Play my turn
     */
    function playCell(uint x, uint y) public {
        require(stage==Stages.started);
        require(x < boardWidth && y < boardWidth);
        require(msg.sender == player1 || msg.sender == player2);
        require(checkMyTurn());
        require(_getCell(x,y) == 0);
        _setCell(x,y,nextTurn);
        _passTurn();
        updateState();
    }
    
    function updateState() internal {
        require(stage == Stages.started);
        if(isWin(1))
        {
            player1.transfer(reward);
            stage = Stages.player1Won;
        }
        if(isWin(2))
        {
            player2.transfer(reward);
            stage = Stages.player2Won;
        }
        //Check for blank cells
        for(uint i = 0; i < boardWidth*boardWidth; i++)
        {
            if(cells[i] == 0)
            {
                return;  // Game still on
            }
                
        }
        stage = Stages.drawn;
    }
    
    /**
     * Retrieve status of game
     */
    function getStatus() constant returns (Stages, address, address, uint) {
         require(msg.sender == player1 || (stage == Stages.prejoin || msg.sender == player2));
         return (stage, player1, player2, reward);
    }
    
    function isWin(uint player) internal constant returns (bool) {
        // Check rows
        for(uint y = 0; y < boardWidth; y++){
            bool failed = false;
            for(uint x = 0; x < boardWidth; x++){
                if(_getCell(x,y) != player)
                {
                    failed = true;
                    break;
                }
            }
            if(!failed)
                return true;
        }
        
        //Check columns
        for(x = 0; x < boardWidth; x++){
            failed = false;
            for(y = 0; y < boardWidth; y++){
                if(_getCell(x,y) != player)
                {
                    failed = true;
                    break;
                }
            }
            if(!failed)
                return true;
        }
        
        // Positive Diagonal
        failed = false;
        for(x = 0; x < boardWidth; x++)
        {
            if(_getCell(x,x) != player)
            {
                failed = true;
                break;
            }
        }
        if(!failed)
            return true;
            
        // Negative Diagonal
        failed = false;
        for(x = 0; x < boardWidth; x++)
        {
            if(_getCell(boardWidth - x - 1,x) != player)
            {
                failed = true;
                break;
            }
        }
        if(!failed)
            return true;
        
    }
}

TransferLearn.sol

pragma solidity ^0.4.16;

contract TransferLearn
{
    mapping (address => uint) balance;
    
    function accept() payable {
        require(msg.value == 2 ether);
        balance[msg.sender] += msg.value;
    }
    
    
    function getBalance() public constant returns (uint) {
        return balance[msg.sender];
    } 
    
    function refund(uint amountRequested) public {
      require(amountRequested > 0 && amountRequested <= balance[msg.sender]);
    
      balance[msg.sender] -= amountRequested;
    
      msg.sender.transfer(amountRequested); // contract transfers ether to msg.sender's address
    }
    
}