C# 测试整数列表是奇数还是偶数
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原文地址: http://stackoverflow.com/questions/18818680/
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Testing if a list of integer is odd or even
提问by Arthur Mamou-Mani
Trying to determine if my list of integer is made of odd or even numbers, my desired output is a list of true an/or false. Can I perform the following operation on the list lst or do I need to create a loop? A is the output.
试图确定我的整数列表是由奇数还是偶数组成，我想要的输出是真和/或假的列表。我可以对列表 lst 执行以下操作还是需要创建一个循环？A是输出。
List <int> lst = new List <int>();
A = IsOdd(lst);
采纳答案by Michael0x2a
You could try using Linq to project the list:
您可以尝试使用 Linq 来投影列表：
var output = lst.Select(x => x % 2 == 0).ToList();
This will return a new list of bools such that {1, 2, 3, 4, 5}will map to {false, true, false, true, false}.
这将返回一个新的 bool 列表，以便{1, 2, 3, 4, 5}映射到{false, true, false, true, false}.
回答by TGH
Just use the modulus
只需使用模数
loop through the list and run the following on each item
循环遍历列表并对每个项目运行以下命令
if(num % 2 == 0)
{
//is even
}
else
{
//is odd
}
Alternatively if you want to know if all are even you can do something like this:
或者，如果您想知道是否全部都是偶数，您可以执行以下操作：
bool allAreEven = lst.All(x => x % 2 == 0);
回答by Free Coder 24
There's at least 7 different ways to test if a number is odd or even. But, if you read through these benchmarks, you'll find that as TGH mentioned above, the modulus operation is the fastest:
至少有 7 种不同的方法可以测试一个数字是奇数还是偶数。但是，如果您阅读这些基准测试，您会发现正如上面提到的 TGH，取模运算是最快的：
if (x % 2 == 0)
//even number
else
//odd number
Here are a few other methods (from the website) :
以下是其他一些方法（来自网站）：
//bitwise operation
if ((x & 1) == 0)
//even number
else
//odd number
//bit shifting
if (((x >> 1) << 1) == x)
//even number
else
//odd number
//using native library
System.Math.DivRem((long)x, (long)2, out outvalue);
if ( outvalue == 0)
//even number
else
//odd number
回答by Newby25
#region even and odd numbers
for (int x = 0; x <= 50; x = x + 2)
{
int y = 1;
y = y + x;
if (y < 50)
{
Console.WriteLine("Odd number is #{" + x + "} : even number is #{" + y + "} order by Asc");
Console.ReadKey();
}
else
{
Console.WriteLine("Odd number is #{" + x + "} : even number is #{0} order by Asc");
Console.ReadKey();
}
}
//order by desc
for (int z = 50; z >= 0; z = z - 2)
{
int w = z;
w = w - 1;
if (w > 0)
{
Console.WriteLine("odd number is {" + z + "} : even number is {" + w + "} order by desc");
Console.ReadKey();
}
else
{
Console.WriteLine("odd number is {" + z + "} : even number is {0} order by desc");
Console.ReadKey();
}
}
回答by user9667279
--simple codes--
--简单代码--
#region odd / even numbers order by desc
//declaration of integer
int TotalCount = 50;
int loop;
Console.WriteLine("\n---------Odd Numbers -------\n");
for (loop = TotalCount; loop >= 0; loop--)
{
if (loop % 2 == 0)
{
Console.WriteLine("Even numbers : #{0}", loop);
}
}
Console.WriteLine("\n---------Even Numbers -------\n");
for (loop = TotalCount; loop >= 0; loop--)
{
if (loop % 2 != 0)
{
Console.WriteLine("odd numbers : #{0}", loop);
}
}
Console.ReadLine();
#endregion
