Amitd - 13 days ago 8
C# Question

Generating all Possible Combinations

Given 2 arrays

`Array1 = {a,b,c...n}`
and
`Array2 = {10,20,15....x}`
how can I generate all possible combination as Strings a(i) b(j) c(k) n(p)
where

``````1 <= i <= 10,  1 <= j <= 20 , 1 <= k <= 15,  .... 1 <= p <= x
``````

Such as:

``````a1 b1 c1 .... n1
a1 b1 c1..... n2
......
......
a10 b20 c15 nx (last combination)
``````

So in all total number of combination = product of elements of
```array2 = (10 X 20 X 15 X ..X x)```

Similar to a Cartesian product, in which the second array defines the upper limit for each element in first array.

Example with fixed numbers,

``````    Array x =  [a,b,c]
Array y =  [3,2,4]
``````

So we will have 3*2*4 = 24 combinations. Results should be:

``````    a1 b1 c1
a1 b1 c2
a1 b1 c3
a1 b1 c4

a1 b2 c1
a1 b2 c2
a1 b2 c3
a1 b2 c4

a2 b1 c1
a2 b1 c2
a2 b1 c3
a2 b1 c4

a2 b2 c1
a2 b2 c2
a2 b2 c3
a2 b2 c4

a3 b1 c1
a3 b1 c2
a3 b1 c3
a3 b1 c4

a3 b2 c1
a3 b2 c2
a3 b2 c3
a3 b2 c4 (last)
``````

``````using System;
using System.Text;

public static string[] GenerateCombinations(string[] Array1, int[] Array2)
{
if(Array1 == null) throw new ArgumentNullException("Array1");
if(Array2 == null) throw new ArgumentNullException("Array2");
if(Array1.Length != Array2.Length)
throw new ArgumentException("Must be the same size as Array1.", "Array2");

if(Array1.Length == 0)
return new string[0];

int outputSize = 1;
var current = new int[Array1.Length];
for(int i = 0; i < current.Length; ++i)
{
if(Array2[i] < 1)
throw new ArgumentException("Contains invalid values.", "Array2");
if(Array1[i] == null)
throw new ArgumentException("Contains null values.", "Array1");
outputSize *= Array2[i];
current[i] = 1;
}

var result = new string[outputSize];
for(int i = 0; i < outputSize; ++i)
{
var sb = new StringBuilder();
for(int j = 0; j < current.Length; ++j)
{
sb.Append(Array1[j]);
sb.Append(current[j].ToString());
if(j != current.Length - 1)
sb.Append(' ');
}
result[i] = sb.ToString();
int incrementIndex = current.Length - 1;
while(incrementIndex >= 0 && current[incrementIndex] == Array2[incrementIndex])
{
current[incrementIndex] = 1;
--incrementIndex;
}
if(incrementIndex >= 0)
++current[incrementIndex];
}
return result;
}
``````
Source (Stackoverflow)