How to make a combination of strings in C#?

问题

I need to make a combinaion of Stings "a" "b" "c" "d". I've tried putting them in a list then parsing a foreach methord through them, but to no avail.

What else can I do?

回答1:

I will give you the logic.

Create a List<String> and then go on adding each string to it.

List<String> s = new List<String>();  

s.add("a");
s.add("b");
s.add("c");
s.add("d");

Once you added all the strings, then generate a random number between minimum and maximum index like this :

private int RandomNumber(int min, int max)
{
Random random = new Random();
return random.Next(min, max); 
}

Then, while printing each string in the loop over the List with this number, be sure to check that the same random number is not repeated for the nex iteration.

回答2:

Having the strings in an array you can use the function below to print all permutations so it outputs: abcd, abdc, adbc, etc.

Recursive permutation (from MSDN):

public static void Permute(string[] strings, int start, int finish)
  {
    if (start == finish)
    {
      for (int i = 0; i <= finish; ++i)
      {
        Console.Write(strings[i] + " " );
      }
        Console.WriteLine("");
    }
    else
    {
      for (int i = start; i <= finish; ++i)
      {
        string temp = strings[start];
        strings[start] = strings[i];
        strings[i] = temp;

        Permute(strings, start+1, finish);

        temp = strings[start];
        strings[start] = strings[i];
        strings[i] = temp;
      }
    }

  }  // Permute()

回答3:

Will a list do you?

List<String>myStrings = new List<String>();

myStrings.Add("a");
...
myStrings.Add("d");

You should be able to loop through that

回答4:

if you have a set number of strings you could use

var s = String.Format("{0}{1}{2}{3}", stringA, stringB, stringC, stringD);

otherwise a for/foreach loop would be the way forward,

var sb = new StringBuilder();
var strings = new List<string>();

// Add strings to list

for (var i = 0; i < strings.Count; i++)
{
    sb.Append(strings[i]);
}

var s = sb.ToString();

I wouldn't use string + string + string style concatenation as this is bad practice due to the way strings work in memory.

EDIT: I haven't tested the code it was written in the browser! let me know if you have any issues.

Just seen the comments above, the code I have posted will always output the strings in the same order so may not be what you want.

HTH

OneShot

回答5:

List<String>stringList = new List<String>();

stringList.Add("a");
stringList.Add("b");
...
...

foreach(string item in stringList)
 {
   string text=item;
}

回答6:

This example does all the combinations (proper):

using System;
using System.Linq;
using System.Collections.Generic;

public static class Program
{
    public static void Main(string[] args)
    {
        var list = new [] { "a", "b", "c", "d" };
        foreach (var combi in Enumerable.Repeat(list, list.Length).CartesianProduct())
            Console.WriteLine(string.Join(" ", combi));
    }

    static IEnumerable<IEnumerable<T>> CartesianProduct<T>(this IEnumerable<IEnumerable<T>> sequences) 
    { 
        IEnumerable<IEnumerable<T>> emptyProduct = new[] { Enumerable.Empty<T>() }; 
        return sequences.Aggregate( 
                emptyProduct, 
                (accumulator, sequence) =>  
                from accseq in accumulator  
                from item in sequence  
                select accseq.Concat(new[] {item}));                
    }
}

Output:

a a a a
a a a b
a a a c
a a a d
a a b a
a a b b
a a b c
a a b d
a a c a
a a c b
....
d d b c
d d b d
d d c a
d d c b
d d c c
d d c d
d d d a
d d d b
d d d c
d d d d

If you needed permutations, you can drop-in an algorithm from

MoreLinq
CodeProject http://www.codeproject.com/KB/recipes/Combinatorics.aspx

来源：https://stackoverflow.com/questions/6276636/how-to-make-a-combination-of-strings-in-c

标签

.net

string

combinations