如何从 C# 中的二维数组获取完整的行或列 [英] How to get a complete row or column from 2D array in C#

问题描述

我不想使用锯齿状数组，我有一个二维数组，我想获得一个完整的列或行，而不需要遍历它.有没有人知道如何做到这一点.

I do not want to use a jagged array and I have a 2D array and I want to get a complete column or row without looping through it. Does anyone have an idea how it can be done.

double [,]  array = new double [3,3] ;

1   2   3 
4   5   6

Out: 1   2   3  or 2   5 

推荐答案

您可以使用 Buffer.BlockCopy() 优化它以获取行，但是要获取列，您必须循环.Buffer.BlockCopy() 最终使用处理器指令复制一块内存，所以速度相当快.

You can optimise it for getting rows by using Buffer.BlockCopy(), but to get a column you'll have to loop. Buffer.BlockCopy() ultimately uses a processor instruction to copy a block of memory, so it is pretty fast.

将代码放入扩展方法中，方便调用.注意Buffer.BlockCopy()只能用于基本类型的数组，即int、double、char 等.这不包括 string.

It's convenient to put the code into an extension method to make it easier to call. Note that Buffer.BlockCopy() can only be used on arrays of primitive types, i.e. int, double, char etc. This does NOT include string.

这是一个可编译的例子:

Here's a compilable example:

using System;
using System.Linq;
using System.Runtime.InteropServices;

namespace ConsoleApplication4
{
    public static class Program
    {
        private static void Main()
        {
            var array = new [,]
            {
                {0.1, 0.2, 0.3, 0.4, 0.5},
                {1.1, 1.2, 1.3, 1.4, 1.5},
                {2.1, 2.2, 2.3, 2.4, 2.5},
                {3.1, 3.2, 3.3, 3.4, 3.5},
            };

            var row = array.GetRow(2);

            // This prints 2.1, 2.2, 2.3, 2.4, 2.5

            Console.WriteLine(string.Join(", ", row.Select(element => element.ToString())));
        }
    }

    public static class ArrayExt
    {
        public static T[] GetRow<T>(this T[,] array, int row)
        {
            if (!typeof(T).IsPrimitive)
                throw new InvalidOperationException("Not supported for managed types.");

            if (array == null)
                throw new ArgumentNullException("array");

            int cols = array.GetUpperBound(1) + 1;
            T[] result = new T[cols];

            int size;

            if (typeof(T) == typeof(bool))
                size = 1;
            else if (typeof(T) == typeof(char))
                size = 2;
            else
                size = Marshal.SizeOf<T>();

            Buffer.BlockCopy(array, row*cols*size, result, 0, cols*size);

            return result;
        }
   }
}

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