Apply Bitwise operator on multiple integers at once

Question

I have a list of integers, that can have any number of items. Now, I want to calculate the BITWISE XOR of all these numbers. If the numbers are already known, this can be done as follows:

int xor = 10 ^ 25 ^ 40 ^ 55......and so on

But when number of elements is unknown, I am not able to achieve it dynamically at the runtime, for each element of the list. I want to apply bitwise XOR to all the times at once, not two at a time.

Answer 1

You can loop over the elements and apply the xor to a result variable, like this:

int[] values = new int[] { 10, 25, 40, 55 };
int xor = values[0];
for(int i = 1; i < values.Length; i++) {
    xor ^= values[i];
}

Due to the interchangable nature of xor, these two approaches have the same result:

// In one line
int xor1 = 10 ^ 25 ^ 40;

// In separate lines
int xor2 = 10 ^ 25;
xor2 ^= 40;

See here: https://dotnetfiddle.net/zqSVad
The actual calculation happening here is exactly the same. You can expand this concept to a loop and have the desired effect.

Answer 2

You can use the Aggregate extension method (from System.Linq) to apply an accumulator function over each item in the array. It works by taking a starting value (we can use 0 in this case, since 0 ^ n == n), and applying the accumulator function for each item in the list.

In our case the accumulator is just adding the XOR of the number with the next value back to the number again:

int[] numbers = {10, 25, 40, 55};
int result = numbers.Aggregate(0, (accumulation, next) => accumulation ^ next);
// result = 12