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用Max(F(X))选择X

linq c#

mpen · 技术社区 · 15 年前

我想为跳棋游戏写些人工智能。我想选择棋盘得分最高的那一步。

需要这样的东西:

var bestMove = from m in validMoves
                where BoardScore(opp, board.Clone().ApplyMove(m)) is max
                select m

Move bestMove = null;
float highestScore = float.MinValue;
foreach (var move in validMoves)
{
    float score = BoardScore(opp, board.Clone().ApplyMove(move));
    if (score > highestScore)
    {
        highestScore = score;
        bestMove = move;
    }
}

4 回复 | 直到 15 年前

Dan Tao 15 年前

你不是基本上已经搞清楚了吗?如果编写自己的扩展方法,则可以以典型的LINQ方式实现此功能:

public static T MaxFrom<T, TValue>(this IEnumerable<T> source, Func<T, TValue> selector, IComparer<TValue> comparer)
{
    T itemWithMax = default(T);
    TValue max = default(TValue);

    using (var e = source.GetEnumerator())
    {
        if (e.MoveNext())
        {
            itemWithMax = e.Current;
            max = selector(itemWithMax);
        }

        while (e.MoveNext())
        {
            T item = e.Current;
            TValue value = selector(item);
            if (comparer.Compare(value, max) > 0)
            {
                itemWithMax = item;
                max = value;
            }
        }
    }

    return itemWithMax;
}

public static T MaxFrom<T, TValue>(this IEnumerable<T> source, Func<T, TValue> selector)
{
    return source.MaxFrom(selector, Comparer<TValue>.Default);
}

这样你就可以做到:

var bestMove = validMoves
    .MaxFrom(m => BoardScore(opp, board.Clone().ApplyMove(m)));

Matthew Flaschen 15 年前

var scores = from m in validMoves
                select BoardScore(opp, board.Clone().ApplyMove(m));
var bestMove = scores.Max();

我本应该仔细阅读的。你可以做:

var descendingMoves = validMoves.OrderByDescending(m=>BoardScore(opp, board.Clone().ApplyMove(m)));
var bestMove = descendingMoves.First();

但这是 O(n log n) blog post 关于这个问题的讨论。它提出了一个 Max

Grozz 15 年前

    float max = validMoves.Max(m => BoardScore(opp, board.Clone().ApplyMove(m)));
    var bestMove = validMoves
          .Where(m => BoardScore(opp, board.Clone().ApplyMove(m)) == max)
          .First();

Nathan Ernst 15 年前

你会想看看 Enumerable.Max(TSource) Method (IEnumerable(TSource), Func(TSource, Single)) . 即。:

var bestMove = validMoves.Max((m)=>BoardScore(opp, board.Clone().ApplyMove(m)));

var scores = from m in validMoves
             select new {Move=m, Score=BoardScore(opp, board.Clone().ApplyMove(m))};
var bestMove = scores.Max(s=>s.Score).Move;

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