Game experience level question

I have an algorithm que开发者_如何学运维stion related to XP levels in games:

I have a table that lists level numbers, and number of XPs in that level:

GameLevel    ExperiencePointsInLevel
1            30
2            70
3            160
4            250

For each player, I only maintain their total XP, not any level info. Given a player's total XP, how do I determine the following via an algorithm (I'm using C# & LINQ)?

1. Current level of person
2. Number points the person has in this level

For example, if a player has 110 XPs, the answer would be:

1. Level 3
2. 10 XPs; (110-30-70 = 10)

Any ideas?

Cheers,

Dean

If experience points in level is changed to represent the total XP a player needs to reach that level.

Game Level    Experience Points
 1             0
 2             100
 3             200
 4             400

A more functional approach with LINQ would be something like the following:

var playerlevel = ExperiencePointsTable
    .Where(xpt => xpt.ExperiencePointsInLevel <= player.ExperiencePoints)
    .Select(xpt => xpt.GameLevel)
    .Max();

I think this simplifies the solution and avoids having to generate arrays for a look up.

Edit: fixed to check less than or equal to level.

To find out how many xp the player has to get to the next level you can use a similiar LINQ query.

var xpToNextLevel = (ExperiencePointsTable
    .Where(xpt => xpt.ExperiencePointsInLevel > player.ExperiencePoints)
    .Select(xpt => xpt.ExperiencePoints)
    .Min()) - player.ExperiencePoints;

You can keep a list of the upper inclusive bound of each level (Level 1: 0-29, Level 2: 30-99, etc.) and perform a binary search for the input value:

var levels = new int[]
{
    0 - 1,
    30 + 0 - 1,
    70 + 30 + 0 - 1,
    160 + 70 + 30 + 0 - 1,
    250 + 160 + 70 + 30 + 0 - 1
};

var input = 110;

var level = Array.BinarySearch(levels, input);
if (level < 0)
    level = ~level;

Console.WriteLine("Level: {0}", level);
Console.WriteLine("Points: {0}", input - (levels[level - 1] + 1));

(untested; may contain off-by-one errors)

If the table is sorted, then do something like this:

foreach(DataRow row in table.Rows)
{
    if(xp > (int)row["XP"])
    {
        xp -= (int)row["XP"];
    } else {
        Console.WriteLine("Level: " + row["Level"] + " with " + xp + " xp");
        break;
    }
}

Same idea with whatever data structure you're using