Question

我遇到的问题是我不确定如何将我的#include <iostream> #include <memory> struct Base { virtual void print()=0; virtual ~Base(){} }; struct Derived: public Base { void print(){std::cout << "this is Derived\n";} }; struct Foo { Foo(std::unique_ptr<Base>&& r): bref{std::move(r)} {} void print(){ bref->print(); } std::unique_ptr<Base> bref; }; int main() { Foo f{std::unique_ptr<Derived>(new Derived)}; //or make_unique f.print(); }数组转换为double。我有一些非常笨拙的LINQ Dictionary语句，因此我想使用Where的键来查找特定值。我有两个类，分别是getter和setter，然后是计算器。

我在尝试进行查找或Dictionary时花了些力气，但没有任何运气。

Dictionary

Answer 1

您可以在循环之前按OriginYear和DevelopmentYear对产品进行分组。这样的事情可能会有所帮助：

public IList<double> Calculate(Product product)
{
    IList<double> cumulativeDataTriangle = new List<double>();
    if (!product.ProductIncrementalValues.Any())
        return cumulativeDataTriangle;

    var lookup = product.ProductIncrementalValues.ToLookup(v => (v.OriginYear, v.DevelopmentYear), v => v.IncrementalValue); 
    for (int i = 0; i < product.NoOfDevelopmentYears; i++)
    {
        var originYear = product.EarliestOriginYear + i;
        double previous = 0;
        for (int j = 0; j < product.NoOfDevelopmentYears - i; j++)
        {
            var developmentYear = originYear + j;
            var incrementalValues = lookup[(originYear, developmentYear)];
            double incrementalValue = incrementalValues.FirstOrDefault();

            var tmp = incrementalValue + previous;
            cumulativeDataTriangle.Add(tmp);
            previous = tmp;
        }
    }

    return cumulativeDataTriangle;
}

Answer 2

由于上一个答案，我设法基于Dictionary和OriginYear实现了DevelopmentYear，并返回了IncrementalValue。

public IList<double> Calculate(Product product)
        {
            IList<double> cumulativeDataTriangle = new List<double>();
            if (!product.ProductIncrementalValues.Any())
                return cumulativeDataTriangle;

            var lookup = product.ProductIncrementalValues.
                ToDictionary(v => (v.OriginYear, v.DevelopmentYear), v => v.IncrementalValue);
            for (int i = 0; i < product.NoOfDevelopmentYears; i++)
            {
                var originYear = product.EarliestOriginYear + i;
                double previous = 0;
                for (int j = 0; j < product.NoOfDevelopmentYears - i; j++)
                {
                    var developmentYear = originYear + j;
                    double incrementalValue;
                    lookup.TryGetValue((originYear, developmentYear), out incrementalValue);

                    var tmp = incrementalValue + previous;
                    cumulativeDataTriangle.Add(tmp);
                    previous = tmp;
                }
            }

            return cumulativeDataTriangle;
        }

有没有办法将数组翻译成字典

2 个答案: