Dutch National Flag Three Way Partition in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to swap two integers using a temporary variable.

DSA C

void swap(int *a, int *b) {
    int temp = *a;
    *a = [1];
    *b = temp;
}

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A*b

B*a

Ca

Dtemp

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning 'a' instead of '*b'.

Using 'temp' instead of '*b'.

We assign the value pointed by b to the location pointed by a to complete the swap.

2fill in blank

medium

Complete the code to move the 'low' pointer forward when the current element is less than pivot.

DSA C

if (arr[i] < pivot) {
    swap(&arr[i], &arr[[1]]);
    low++;
    i++;
}

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Apivot

Blow

Ci

Dhigh

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping with 'high' instead of 'low'.

Swapping with 'i' which is the current index.

We swap with the element at 'low' pointer and then increment 'low'.

3fill in blank

hard

Fix the error in the loop condition to correctly process all elements.

DSA C

while ([1] <= high) {
    if (arr[i] < pivot) {
        swap(&arr[i], &arr[low]);
        low++;
        i++;
    } else if (arr[i] > pivot) {
        swap(&arr[i], &arr[high]);
        high--;
    } else {
        i++;
    }
}

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Ahigh

Blow

Cpivot

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'low' or 'high' as the loop variable incorrectly.

Comparing 'pivot' instead of an index.

The index 'i' should be compared to 'high' to process all elements.

4fill in blank

hard

Fill both blanks to initialize pointers correctly before the partition loop.

DSA C

int low = [1];
int high = [2];

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A0

B1

Csize - 1

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Setting 'low' to 1 instead of 0.

Setting 'high' to size instead of size - 1.

The 'low' pointer starts at 0 and 'high' at the last index (size - 1).

5fill in blank

hard

Fill all three blanks to complete the Dutch National Flag partition function.

DSA C

void dutch_national_flag(int arr[], int size, int pivot) {
    int low = [1];
    int high = [2];
    int i = [3];

    while (i <= high) {
        if (arr[i] < pivot) {
            swap(&arr[i], &arr[low]);
            low++;
            i++;
        } else if (arr[i] > pivot) {
            swap(&arr[i], &arr[high]);
            high--;
        } else {
            i++;
        }
    }
}

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A0

Bsize - 1

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Starting 'i' or 'low' at 1 instead of 0.

Setting 'high' to size instead of size - 1.

Initialize 'low' and 'i' to 0, and 'high' to size - 1 to cover the whole array.