CODEWITHSUNDEEP
powershell
Learner
Learner

Reputation: 351

Program to print permutation and combination for the given element

I have written the following code in PowerShell to display the permutation and combination for the given string but I am not able to achieve it by recursive functions.

function Swapping1 {
    $a = "abc"
    $b = $a.ToCharArray()
    $c = $b.Length-1
    $d = 0
    GetPer($b, $d, $c)
}

function GetPer {
    Param($list, $k, $m)

    [char[]] $list1 = $list[0]

    $k = $list[1]
    $m = $list[2]

    if ($k -eq $m) {
       # Write-Host $list1
    } else {
        for ($i = $k; $i -le 1; $i++) {
            $a = $list1[$k]
            $b = $list1[$i]

            $a, $b = $b, $a
            $k = $k+1
            Write-Host $list[0]
            GetPer($list[0], $k, $m)
            $a, $b = $b, $a
        }
    }
}

The same logic when I write it in C# it is working fine.

private static void Swap(ref char a, ref char b) {
    if (a == b) return;

    a ^= b;
    b ^= a;
    a ^= b;
}

private static void GetPermutation(char[] list, int k, int m) {
    if (k == m) {
        Console.Write(list);
        Console.WriteLine();
    } else
        for (int i = k; i <= m; i++) {
            Swap(ref list[k], ref list[i]);
            GetPermutation(list, k + 1, m);
            Swap(ref list[k], ref list[i]);
        }
}

static void Main(string[] args) {
    string str = "abc";
    char[] arr = str.ToCharArray();
    int x = arr.Length - 1;
    GetPermutation(arr, 0, x);
    //GetPer(arr);
    Console.Read();
}

Below is the output when I executed the PowerShell script:

PS C:\WINDOWS\system32> C:\Dorababu\Power Shell\Swapping1.ps1
a b c
a b c
a b c

C# output:

enter image description here

Upvotes: 1

Views: 139

Answers (1)

Ansgar Wiechers
Ansgar Wiechers

Reputation: 200213

Your C# and PowerShell code do different things. You output at a different place in PowerShell, the condition in the for loop is different ($i -le 1 vs i <= m), you increment $k in the PowerShell code ($k = $k+1) but not in the C# code, and your swapping as well as the parameter handling are completely wrong. A function call foo(a, b, c) passes an array a, b, c to the first parameter of foo() and nothing to the second and third parameter. The correct way to call foo() with three parameters a, b, and c in PowerShell would be foo a b c. And for swapping array elements simply use the array elements. Don't assign them to variables first.

If you actually implement the same logic the PowerShell code works as expected:

function Swapping1 {
    $a = "abc"
    $b = $a.ToCharArray()
    $c = $b.Length-1
    $d = 0
    GetPer $b $d $c
}

function GetPer {
    Param($list, $k, $m)

    if ($k -eq $m) {
        Write-Host $list
    } else {
        for ($i = $k; $i -le $m; $i++) {
            $list[$k], $list[$i] = $list[$i], $list[$k]
            GetPer $list ($k+1) $m
            $list[$k], $list[$i] = $list[$i], $list[$k]
        }
    }
}

Swapping1

Upvotes: 3

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