C#•12mo ago

❔ Can anyone explain this piece of code

So I found a piece of code online that solves my problem, but I have to understand how it works before being able to modify it to fit my needs. Can anyone tell me what the FindCloseTriplet() function is actually doing? I found it confusing to read. https://www.geeksforgeeks.org/find-a-triplet-in-an-array-whose-sum-is-closest-to-a-given-number/amp/?fbclid=IwAR30br4s6ta3oq9O1IwhSWCD6E25hzk1ulSUPfiAjQcSQvyIuJcXXlN2C10

7 Replies

boiled goose•12mo ago

have you tried it?

EmperMiner•12mo ago

Yes I have, it works but I don't know what it's actually doing. The website displays the addition step of the triplets but I don't see anything being added in the code And yes, I am very bad at C# but good enough to make games

benqbenq•12mo ago

If you are talking about the algorithm itself, I don't think I can help you because: 1) recursive functions are hard to track 2) I'm DUM The "ref" keyword means the value is passed by reference: so when some recursive call stop at some point and start going backwards to the initial caller, the intermediate calculated values (with "ref" keyword ones) will be not the same, as they were before stepping into this recursive call. To illustrate, here's an example:

int initialValueToCalculate = 1;
Example(0, ref initialValueToCalculate);
Console.WriteLine(initialValueToCalculate); // 8

static void Example(int currentIteration, ref int someValue)
{
    // Stop on 3rd recursion call
    if (currentIteration == 3)
    {
        return;
    }
    
    someValue *= 2; // Do calculations that will be shared in all recursion steps
    Example(++currentIteration, ref someValue);
}

int initialValueToCalculate = 1;
Example(0, ref initialValueToCalculate);
Console.WriteLine(initialValueToCalculate); // 8

static void Example(int currentIteration, ref int someValue)
{
    // Stop on 3rd recursion call
    if (currentIteration == 3)
    {
        return;
    }
    
    someValue *= 2; // Do calculations that will be shared in all recursion steps
    Example(++currentIteration, ref someValue);
}

The king of kings•12mo ago

You're not a lone, we all struggle in c#

benqbenq•12mo ago

If you want to understand the algorithm, I can only suggest you to ask ChatGPT not to explain(as its makes mistakes often), but at least to format the code, so its easier to read. Here's formatted one:

int[] arr = new int[] { -1, 2, 1, -4 };
int target = 1;
int arrSize = arr.Length;
int minDiff = int.MaxValue;
int answer = 0;

FindClosestTriplet(
    arr,
    size: arrSize,
    targetSum: target,
    currentCount: 0, 
    currentSum: 0, 
    currentIndex: 0, 
    closestSum: ref answer,
    minDifference: ref minDiff);

Console.WriteLine(answer);

static void FindClosestTriplet(int[] array, int size, int targetSum, int currentCount, int currentSum, int currentIndex, ref int closestSum, ref int minDifference)
{
    // Return when reaching the end of the array
    // If we have picked three elements so far, check if the sum is closest to our "targetSum"
    if (currentIndex == size)
    {
        if (currentCount == 3)
        {
            int currentDifference = Math.Abs(targetSum - currentSum);
            if (currentDifference < minDifference)
            {
                minDifference = currentDifference;
                closestSum = currentSum;
            }
        }
        return;
    }

    // Pick this number
    FindClosestTriplet(array, size, targetSum, currentCount + 1, currentSum + array[currentIndex], currentIndex + 1, ref closestSum, ref minDifference);

    // Don't pick this number
    FindClosestTriplet(array, size, targetSum, currentCount, currentSum, currentIndex + 1, ref closestSum, ref minDifference);
}

int[] arr = new int[] { -1, 2, 1, -4 };
int target = 1;
int arrSize = arr.Length;
int minDiff = int.MaxValue;
int answer = 0;

FindClosestTriplet(
    arr,
    size: arrSize,
    targetSum: target,
    currentCount: 0, 
    currentSum: 0, 
    currentIndex: 0, 
    closestSum: ref answer,
    minDifference: ref minDiff);

Console.WriteLine(answer);

static void FindClosestTriplet(int[] array, int size, int targetSum, int currentCount, int currentSum, int currentIndex, ref int closestSum, ref int minDifference)
{
    // Return when reaching the end of the array
    // If we have picked three elements so far, check if the sum is closest to our "targetSum"
    if (currentIndex == size)
    {
        if (currentCount == 3)
        {
            int currentDifference = Math.Abs(targetSum - currentSum);
            if (currentDifference < minDifference)
            {
                minDifference = currentDifference;
                closestSum = currentSum;
            }
        }
        return;
    }

    // Pick this number
    FindClosestTriplet(array, size, targetSum, currentCount + 1, currentSum + array[currentIndex], currentIndex + 1, ref closestSum, ref minDifference);

    // Don't pick this number
    FindClosestTriplet(array, size, targetSum, currentCount, currentSum, currentIndex + 1, ref closestSum, ref minDifference);
}

Also, you can use the debugger in VS or some other IDE to track the intermediate values.

EmperMiner•12mo ago

thank you for the explaination of ref, I still can't understand the code though. I'll keep trying

Accord•12mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Can anyone explain this piece of code