使用Linq减去两个数组

Question

I've two arrays arr1 and arr2 of the following type

class Data
{
  public int IdProduct;
  public double Price;
}

and I need to subtract the Price of arr2 to arr1 but the items of the arrays are the result of different queries so the amount of products in arr1 not necessarily match the amount of products in arr2 and there're no duplicated products in the arrays.

I need to do the subtraction product by product in each array, ie.

var total =
  from a1 in arr1
  join a2 in arr2 on a1.IdProducto equals a2.IdProducto
  select new
  {
    Product = a1.IdProduct,
    Price = a1.Price - a2.Price
  };

Answer 1

Something like this?

var q = from a in arr1
                  join b in arr2 on a.IdProduct equals b.IdProduct into c
              from x in c.DefaultIfEmpty()
              select new Data {
                IdProduct = a.IdProduct,
                Price = x == null ? a.Price : a.Price - x.Price
              };

arr1 = q.ToArray();

Answer 2

var result = arr1.Concat(arr2)
            .GroupBy(d => d.IdProduct)
            .Select(x => new Data
            {
                IdProduct = x.Key,
                Price = x.Select((y,i) => i == 0 ? y.Price : -y.Price).Sum()
            }).ToList();

Answer 3

You have two arrays of Data with a total price difference ?

arr1.Sum(d => d.Price) - arr2.Sum(d => d.Price);

Basically this code sums up both arrays and subtracts afterwards. The total effort is therefore linearly growing with the length of the arrays: O(n+m) .