address[] public validatorList = [<your first validator address>];
address[] public pendingList = [<your first validator address>];

mapping(address => bool) public isAdmin;

modifier onlyAdmin() {
    require(isAdmin[msg.sender] == true);
    _;
}

event validatorAdded(address newvalidator);
event validatorRemoved(address oldvalidator);
event adminAdded(address newadmin);
event adminRemoved(address oldadmin);
event InitiateChange(bytes32 indexed _parent_hash, address[] _new_set);

function AdminValidatorList() public {
    isAdmin[validatorList[0]] = true;
}

// Called on every block to update node validator list.
function getValidators() public constant returns (address[] _validators) {
    return validatorList;
}

function getPendingValidators() public constant returns (address[] _p) {
    return pendingList;
}

// Add a validator to the list.
function addValidator(address validator) public onlyAdmin {
    for (uint i = 0; i < pendingList.length; i++) {
        require(pendingList[i] != validator);
    }

    pendingList.push(validator);
    validatorAdded(validator);
    InitiateChange(block.blockhash(block.number - 1),pendingList);
}

// Remove a validator from the list.
function removeValidator(address validator) public onlyAdmin returns (bool success){

    uint i=0;
    uint count = pendingList.length;
    success = false;

    // you don't want to leave no validators - can't delete any until you have a minimum of 3.
    // This is in case your 1 remaining node goes down. Leave a safety margin of 2
    if (count > 2) {
        for (i=0; i<count;i++) {
            if (pendingList[i] == validator) {
                if (i < pendingList.length-1) {
                    pendingList[i] = pendingList[pendingList.length-1];
                }
                pendingList.length--;
                success = true;
                validatorRemoved(validator);
                InitiateChange(block.blockhash(block.number - 1),pendingList);
                break;
            }
        }
    }
    return success;
}

// Add an admin.
function addAdmin(address admin) public onlyAdmin {
    isAdmin[admin] = true;
    adminAdded(admin);
}

// Remove an admin.
function removeAdmin(address admin) public onlyAdmin {
    isAdmin[admin] = false;
    adminRemoved(admin);
}

function finalizeChange() public {
    validatorList = pendingList;
}