Classic case of solidity - Smart games

Refer to https://ke.qq.com/webcourse/2379017/103111126#taid=10365401060101385&vid=5285890802017890711

1. Case function introduction

1. Platform parties deploy smart contracts , The user selects the next big or the next small .
2. Smart contracts specify the rules of the game , Using simple random numbers to achieve .

2. The specific code is as follows

pragma solidity ^0.6.1;

struct User{
    
    address  payable addr;
    uint256 amount;
}

contract bocai_demo{
    
    User[] bigs;// Xiada 
    User[] smalls;// Next little 
    address admin;// Address of Platform party 
    bool isFinshed;// End flag 
    uint256 outtimes;// By the time 
    uint256 bigTotalAmount;// Bet a large sum of money 
    uint256 smallTotalAmount;// Bet on a small total amount 
    uint256 result;// The lottery results 
    constructor() public{
    
        admin = msg.sender;
        isFinshed = false;
        outtimes = now+120;// Bet for a minute 
        bigTotalAmount=0;
        smallTotalAmount=0;
    }
    // Bets 
    function bet(bool flag) public payable{
    
        require(msg.value>0,"msg.value must >0");
        require(!isFinshed,"game must not finshed");
        require(now <= outtimes,"time not out");
        if(flag){
    
            // Xiada 
            User memory user = User(msg.sender,msg.value);
            bigs.push(user);
            bigTotalAmount+=msg.value;
        }else{
    
            // Next little 
            User memory user = User(msg.sender,msg.value);
            smalls.push(user);
            smallTotalAmount+=msg.value;
        }
    }
    // A prize 
    function open() public payable{
    
     require(!isFinshed,"only open once");
     require(outtimes<=now,"time must ok");
     // Calculate whether the bet is big or small , Make rules of the game 
     isFinshed=true;
     // Random generation 0-18 Number within ,0-9： Small  10-17： Big 
      result = uint256(keccak256(abi.encode(msg.sender,now,outtimes,admin,smalls.length)))%18;
     // Pie Award 
     User memory user;
     if(result<9){
    
         // Bet a small win 
         for(uint256 i = 0;i < smalls.length;i++){
    
             user=smalls[i];
             // Win a large sum of 90% The money 
             uint256 amount = bigTotalAmount * user.amount / smallTotalAmount *90 /100 + user.amount;
             user.addr.transfer(amount);
           }
         }else{
    
             // Make a big bet 
             for(uint256 i=0;i<bigs.length;i++){
    
                 user=bigs[i];
                 // Win a small sum of 90% The money 
                 uint256 amount = smallTotalAmount * user.amount / bigTotalAmount *90 /100 +user.amount;
                 user.addr.transfer(amount);
             }
         }
    }
    // Get the total amount of money and the remaining money to deploy the contract 
     function getBalance() external view returns(uint256,uint256,uint256){
    
         return (bigTotalAmount,smallTotalAmount,address(this).balance);
     }
    // Get the result of the final game 
     function getResult() external view returns(string memory){
    
         require(isFinshed,"bet must finshed");
         if(result<9){
    
             return "small";
         }else{
    
             return "big";
         }
     }
}

3. The test steps are as follows

1. selection 7 An account address ,1 User deployment contracts , Act as the platform side , rest 6 As a betting user .
   
2. Enter the bet amount and amount as shown in the figure above (true)/ Small (false)
   
3. This is a screenshot of the account address balance transformation during each test
4. After the game , Conduct lottery , The ultimate winner is the big bet , Will get a bet for a small total amount of 90% Reward