Given an array S of n integers, are there elements x, y, z in S such that x + y + z = 0? Find all unique triplets in the array which gives the sum of zero.

Note:

• Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c)
• The solution set must not contain duplicate triplets.
  
  一个重要的优化就是如果上个数已经求过集合了 例如[-1 -1 0 2 2]已经包含了[-1 0 2 2] 当然也包含了 [-1 0 2]集合的。

Posted by: Duncan Mackenzie, MSDN
This post applies to Visual C# .NET 2002/2003

Suppose you want to run a command line application, open up another Windows program, or even bring up the default web browser or email program... how can you do this from your C# code?

The answer for all of these examples is the same, you can use the classes and methods in System.Diagnostics.Process to accomplish these tasks and more.

Example 1. Running a command line application, without concern for the results:

private void simpleRun_Click(object sender, System.EventArgs e){
 System.Diagnostics.Process.Start(@"C:\listfiles.bat");
}

Example 2. Retrieving the results and waiting until the process stops (running the process synchronously):

private void runSyncAndGetResults_Click(object sender, System.EventArgs e){
 System.Diagnostics.ProcessStartInfo psi =
   new System.Diagnostics.ProcessStartInfo(@"C:\listfiles.bat");
 psi.RedirectStandardOutput = true;
 psi.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
 psi.UseShellExecute = false;
 System.Diagnostics.Process listFiles;
 listFiles = System.Diagnostics.Process.Start(psi);
 System.IO.StreamReader myOutput = listFiles.StandardOutput;
 listFiles.WaitForExit(2000);
 if (listFiles.HasExited)
  {
  string output = myOutput.ReadToEnd();
  this.processResults.Text = output;
 }
}

 Example 3. Displaying a URL using the default browser on the user's machine:

private void launchURL_Click(object sender, System.EventArgs e){
 string targetURL = @http://www.duncanmackenzie.net;
 System.Diagnostics.Process.Start(targetURL);
}

In my opinion, you are much better off following the third example for URLs, as opposed to executing IE with the URL as an argument. The code shown for Example 3 will launch the user's default browser, which may or may not be IE; you are more likely to provide the user with the experience they want and you will be taking advantage of the browser that is most likely to have up-to-date connection information.

C# code download available from http://www.duncanmackenzie.net/Samples/default.aspx

By the way, this post is a simple port of an earlier VB FAQ post... just in case you thought you had seen it already in your feeds...