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Comments on How do I filter an array in C?

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How do I filter an array in C?

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No, I'm not trying to get the full program written completely in C by you guys. I only need some way to implement the functionalities of each function I found confusing.

In this challenge in Code Golf CD, I have to make a program that computes the determinant of a two-dimensional array. It also has a program written in JavaScript that solves the challenge which looks like this:

function laplaceDet(matrix) {
	if (matrix.length === 1) return matrix[0][0];

	let sum = 0;
	for (let rowIndex = 0; rowIndex < matrix.length; ++rowIndex) {
		let minorMatrix = matrix.filter((_, index) => index !== rowIndex)
			          .map(row => row.slice(1));
		sum += ((-1) ** rowIndex) * matrix[rowIndex][0] * laplaceDet(minorMatrix);
	}
	return sum;
}

I want to challenge myself into using C for solving the challenge. First, I'll need to reimplement the program, whereas the golfing part will be dealt with later, although I've already been golfing it. Here's what I got so far.

Why'd I stop? There's a function named filter() and I'm not so sure how to get it implemented, and since C has no maps (at least I think none exist in C), it's also difficult to complete the program without it.

So I'll have to improvise... How? How do I implement the filter() method, maybe without using a function to save bytes, and what's a C equivalent to the line of code matrix.filter((_, index) => index !== rowIndex).map(row => row.slice(1));?

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1 comment thread

I don't know how you normally approach those things. I usually start with getting something working b... (2 comments)
I don't know how you normally approach those things. I usually start with getting something working b...
elgonzo‭ wrote about 3 years ago · edited about 3 years ago

I don't know how you normally approach those things. I usually would start with aiming to get something working by implementing the functions you are asking about based on their documented behavior as described in the (official) documentation. At that point, i might as well already inline the predicates/callbacks in the code of the respective functions. Only if i got it working, i would think about how i could possibly optimize (or even significantly rewrite) the code to achieve whatever goals.

General Sebast1an‭ wrote about 3 years ago

elgonzo‭ How do I approach such tasks? I observe what's going on and try to represent it, and if I can't figure out how to properly make it, I look for some advice. The documentation's might help.