我有一个像"1,2,3,4,5,6,7"这样的字符串。
总是7个数字！由,
将它分成2个整数数组的最佳方法是什么，
firts数组包含1-5个数字
第二个数组包含6-7个数字
感谢
答案 0 :(得分：10)
var numString = "1,2,3,4,5,6,7";
var numArray = numString.Split(',');
var array1 = numArray.Take(5).ToArray();
var array2 = numArray.Skip(5).ToArray();
或者如果你想要一个int s的数组。
var numString = "1,2,3,4,5,6,7";
var numArray = numString.Split(',');
var array1 = numArray.Take(5).Select(s => int.Parse(s)).ToArray();
var array2 = numArray.Skip(5).Select(s => int.Parse(s)).ToArray();
请注意，如果您不需要数组，则可以跳过.ToArray()。
修改
实际上，我能想出的最快的代码是
var numString = "1,2,3,4,5,6,7";
var numArray = numString.Split(',');
var array1 = new int[5];
var array2 = new int[2];
array1[0] = int.Parse(numArray[0]);
array1[1] = int.Parse(numArray[1]);
array1[2] = int.Parse(numArray[2]);
array1[3] = int.Parse(numArray[3]);
array1[4] = int.Parse(numArray[4]);
array2[0] = int.Parse(numArray[5]);
array2[1] = int.Parse(numArray[6]);
比第一版快约60％
我比较了Jason版本的速度，选择后有和没有ToArray的速度都慢了15-20％。
第一个因为int.Parse()被称为12次而不是7次，第二次是因为额外的.ToArray()。
这是我的基准代码
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace Stackoverflow_Test
{
class TestToArrayVsEnumerator
{
private const string numString = "1,2,3,4,5,6,7";
private readonly string[] numArray;
private const int iterations = 100000;
private const int numTests = 10;
public TestToArrayVsEnumerator()
{
numArray = numString.Split(',');
}
public void Run()
{
System.Threading.Thread.CurrentThread.Priority = System.Threading.ThreadPriority.Highest;
Console.WriteLine("Warmup");
RunTest(WithEnumerator);
RunTest(WithSelectFirst);
RunTest(WithSelectToArray);
RunTest(StraightForward);
Console.WriteLine("--- test start ---");
StringBuilder sb = new StringBuilder();
foreach (var t in Enumerable.Range(0, numTests))
{
var timeEnumerator = RunTest(WithEnumerator);
var timeWithSelectFirst = RunTest(WithSelectFirst);
var timeWithSelectToArray = RunTest(WithSelectToArray);
var timeStraightForward = RunTest(StraightForward);
sb.AppendLine("WithEnumerator, " + timeEnumerator.TotalMilliseconds + " ms. "
+ "WithSelectFirst, " + timeWithSelectFirst.TotalMilliseconds + " ms. (" + ((100 * ((double)timeWithSelectFirst.Ticks / (double)timeEnumerator.Ticks)) - 100) + "%) "
+ "WithSelectToArray, " + timeWithSelectToArray.TotalMilliseconds + " ms. (" + ((100 * ((double)timeWithSelectToArray.Ticks / (double)timeEnumerator.Ticks)) - 100) + "%) "
+ "StraightForward, " + timeStraightForward.TotalMilliseconds + " ms. (" + ((100 * ((double)timeStraightForward.Ticks / (double)timeEnumerator.Ticks)) - 100) + "%) "
);
}
Console.WriteLine(sb.ToString());
MessageBox.Show(sb.ToString());
Console.WriteLine("--- test end ---");
}
private TimeSpan RunTest(Action test)
{
System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
sw.Start();
foreach (var i in Enumerable.Range(0, iterations))
{
test();
}
sw.Stop();
return sw.Elapsed;
}
public void WithEnumerator()
{
var array1 = numArray.Take(5).Select(s => int.Parse(s)).ToArray();
var array2 = numArray.Skip(5).Select(s => int.Parse(s)).ToArray();
}
public void WithSelectFirst()
{
var intArray = numArray.Select(s => int.Parse(s)).ToArray();
var array1 = numArray.Take(5).ToArray();
var array2 = numArray.Skip(5).ToArray();
}
public void WithSelectToArray()
{
var intArray = numArray.Select(s => int.Parse(s)).ToArray();
var array1 = numArray.Take(5).ToArray();
var array2 = numArray.Skip(5).ToArray();
}
public void StraightForward()
{
var array1 = new int[5];
var array2 = new int[2];
array1[0] = int.Parse(numArray[0]);
array1[1] = int.Parse(numArray[1]);
array1[2] = int.Parse(numArray[2]);
array1[3] = int.Parse(numArray[3]);
array1[4] = int.Parse(numArray[4]);
array2[0] = int.Parse(numArray[5]);
array2[1] = int.Parse(numArray[6]);
}
}
}
结果（发布代码，无调试启动）
WithEnumerator, 446,3176 ms. WithSelectFirst, 538,4354 ms. (20,639517688749%) WithSelectToArray, 505,5178 ms. (13,2641419473487%) StraightForward, 178,6037 ms. (-59,9828238904314%)
WithEnumerator, 445,463 ms. WithSelectFirst, 528,0676 ms. (18,5435378471388%) WithSelectToArray, 525,6011 ms. (17,9898442743842%) StraightForward, 181,1559 ms. (-59,3331208203599%)
WithEnumerator, 454,5901 ms. WithSelectFirst, 526,0643 ms. (15,722779708577%) WithSelectToArray, 524,5135 ms. (15,3816372155927%) StraightForward, 185,8895 ms. (-59,1083263801829%)
WithEnumerator, 442,4805 ms. WithSelectFirst, 525,8961 ms. (18,8518138087441%) WithSelectToArray, 558,0706 ms. (26,1232076893784%) StraightForward, 208,8639 ms. (-52,7970385135616%)
WithEnumerator, 454,3597 ms. WithSelectFirst, 528,4238 ms. (16,3007634699997%) WithSelectToArray, 531,6279 ms. (17,0059536530198%) StraightForward, 185,5925 ms. (-59,1529574475905%)
WithEnumerator, 452,76 ms. WithSelectFirst, 542,3876 ms. (19,7958300203198%) WithSelectToArray, 553,0012 ms. (22,1400300379892%) StraightForward, 184,5231 ms. (-59,2448316989133%)
WithEnumerator, 468,6732 ms. WithSelectFirst, 528,5409 ms. (12,7738688706758%) WithSelectToArray, 549,7821 ms. (17,3060674260871%) StraightForward, 188,0931 ms. (-59,8668965923377%)
WithEnumerator, 489,7136 ms. WithSelectFirst, 560,0267 ms. (14,3580043519314%) WithSelectToArray, 556,3374 ms. (13,6046456541129%) StraightForward, 177,8818 ms. (-63,6763610404122%)
WithEnumerator, 462,5361 ms. WithSelectFirst, 552,7817 ms. (19,5110392464502%) WithSelectToArray, 548,7365 ms. (18,6364696723131%) StraightForward, 180,1382 ms. (-61,054239874466%)
WithEnumerator, 462,787 ms. WithSelectFirst, 536,089 ms. (15,8392521829697%) WithSelectToArray, 543,2204 ms. (17,3802202741218%) StraightForward, 180,4709 ms. (-61,0034637965198%)
答案 1 :(得分：4)
string someString = "1,2,3,4,5,6,7";
var numbers = someString.Split(',')
.Select(s => Int32.Parse(s));
int[] firstFive = numbers.Take(5).ToArray();
int[] afterFirstFive = numbers.Skip(5).ToArray();
答案 2 :(得分：2)
var n = "1,2,3,4,5,6,7".Split(',');
var first5 = n.Take(5).ToArray();
var last2 = n.Skip(5).ToArray();
如果你想将它们转换为整数，你可以这样做：
string x = "1,2,3,4,5,6,7";
var f = x.Split(',').Take(5).Select(s => { int v; if (!Int32.TryParse(s, out v)) v = -1; return v; });
var g = x.Split(',').Skip(5).Select(s => { int v; if (!Int32.TryParse(s, out v)) v = -1; return v; });