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c#foreach
Simon
Simon

Reputation: 19

multiplying each element in array by all array elements, except itself

I need to make a loop that multiply each element in an array by all array elements, except itself .

Example ->

[1 3 4]

[1 3 4]

1 3, 1 4, 3 1, 3 4, 4 1, 4 3

I've wrote the following code:

foreach (int first in Array)
     foreach (int second in Array)
        Console.WriteLine(first + " " + second );

The code that I wrote multiplies every number with itself and the other elements.

any ideas on how to fix this?

Thanks

Upvotes: 0

Views: 1158

Answers (3)

mshwf
mshwf

Reputation: 7469

Another approach that you can use:

    int[] lst = new int[] { 2, 3, 4 };

    int[] multipliedList = new int[lst.Length * (lst.Length - 1)];
    int idx = 0;
    for (int i = 0; i < lst.Length; i++)
    {
        int currIdx = 0;
        foreach (var item in lst)
        {
            if (i != currIdx)
            {
                multipliedList[idx] = lst[i] * item;
                idx++;
            }
            currIdx++;

        }
    }

Upvotes: 0

rossum
rossum

Reputation: 15683

Try nested for loops, with two indexes:

for (int ix1 = 0; ix1 < myArray.Length; ix1++) {
  // Numbers before ix1.
  for (int ix2 = 0; ix2 < ix1; ix2++) {
    Console.WriteLine(myArray[ix1] + " " + myArray[ix2]);
  }
  // Numbers after ix1
  for (int ix2 = ix1 + 1; ix2 < myArray.Length; ix2++) {
    Console.WriteLine(myArray[ix1] + " " + myArray[ix2]);
  }
}

I am more used to Java than C#, so best check my syntax for Javaisms.

Upvotes: 0

Sweeper
Sweeper

Reputation: 274835

You should loop through the indices of the array instead of its elements. This way, you can check whether you are dealing with the same element by checking whether the two indices are equal:

var arr = new int[] {1, 3, 4};
var result = new List<string>();
for (int i = 0 ; i < arr.Length ; i++) {
    for (int j = 0 ; j < arr.Length ; j++) {
        if (i != j) {
            result.Add($"{arr[i]} {arr[j]}");
        }
    }
}

Upvotes: 1

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