Leaderboard.sol

pragma solidity 0.4.9;

contract Leaderboard {
    mapping (uint => User) leaderboard;
    
    struct User {
        address user;
        uint score;
    }
    
    function addScore(uint score) returns (bool) {
        if (leaderboard[9].score >= score)
            // user didn't make it into top 10
            return false;
        for (uint i=0; i<10; i++) {
            if (leaderboard[i].score < score) {
                // resort
                if (leaderboard[i].user != msg.sender) {
                    bool duplicate = false;
                    for (uint j=i+1; j<10; j++) {
                        if (leaderboard[j].user == msg.sender) {
                            duplicate = true;
                            delete leaderboard[j];
                        }
                        if (duplicate)
                            leaderboard[j] = leaderboard[j+1];
                        else
                            leaderboard[j] = leaderboard[j-1];
                    }
                }
                // add new highscore
                leaderboard[i] = User({
                    user: msg.sender,
                    score: score
                });
                return true;
            }
            if (leaderboard[i].user == msg.sender)
                // user is alrady in list with higher or equal score
                return false;
        }
    }
}