In this lesson we will walkthrough the solution and discuss the improvements/extensions that can be made to the implementation
The solution is shown below so only look if you have had a go at solving it yourself and make sure to watch the video first
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pragma solidity 0.6.0;
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contract Game {
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bytes32 constant ROCK = "ROCK";
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bytes32 constant PAPER = "PAPER";
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bytes32 constant SCISSORS = "SCISSORS";
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mapping(address => bytes32) public choices;
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function play(bytes32 choice) external {
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require(choices[msg.sender] == bytes32(0)); // make sure player hasnt played before
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choices[msg.sender] = choice;
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}
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function evaluate(
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address alice,
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bytes32 aliceChoice,
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bytes32 aliceRandomness,
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address bob,
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bytes32 bobChoice,
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bytes32 bobRandomness
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) external view returns (address) {
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// make sure the commitment of the choices hold24
require(25
keccak256(abi.encodePacked(aliceChoice, aliceRandomness)) ==
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choices[alice]
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);
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require(30
keccak256(abi.encodePacked(bobChoice, bobRandomness)) ==
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choices[bob]
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);
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if (aliceChoice == bobChoice) {
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return address(0);
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}
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if (aliceChoice == ROCK && bobChoice == PAPER) {
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return bob;
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} else if (bobChoice == ROCK && aliceChoice == PAPER) {
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return alice;
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} else if (aliceChoice == SCISSORS && bobChoice == PAPER) {
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return alice;
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} else if (bobChoice == SCISSORS && aliceChoice == PAPER) {
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return bob;
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} else if (aliceChoice == ROCK && bobChoice == SCISSORS) {
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return alice;
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} else if (bobChoice == ROCK && aliceChoice == SCISSORS) {
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return bob;
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}
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}
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}