Generate All Combinations Sum K in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the recursive function call with the starting index 0.

DSA C

void findCombinations(int* arr, int n, int k, int start, int* combination, int combSize) {
    // recursive code here
}

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    int k = 5;
    int combination[10];
    findCombinations(arr, 5, k, [1], combination, 0);
    return 0;
}

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A1

B0

Ck

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Starting from index 1 skips the first element.

Using k or -1 as start index causes out-of-bound errors.

The recursive function should start checking combinations from index 0 of the array.

2fill in blank

medium

Complete the code to check if the current sum equals the target sum k.

DSA C

void findCombinations(int* arr, int n, int k, int start, int* combination, int combSize) {
    int sum = 0;
    for (int i = 0; i < combSize; i++) {
        sum += combination[i];
    }
    if (sum [1] k) {
        // print combination
        return;
    }
    // continue recursion
}

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A>

B!=

C<

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using > or < causes incorrect matches.

Using != prints wrong combinations.

We want to check if the sum of the current combination exactly equals k.

3fill in blank

hard

Fix the error in the recursive call to avoid infinite recursion by moving the start index forward.

DSA C

for (int i = start; i < n; i++) {
    combination[combSize] = arr[i];
    findCombinations(arr, n, k, [1], combination, combSize + 1);
}

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Ai + 1

Bi

Cstart

DcombSize

Attempts:

3 left

💡 Hint

Common Mistakes

Using start causes infinite recursion.

Using i or combSize causes wrong indices.

To avoid repeating the same element, the next recursive call should start from the next index i + 1.

4fill in blank

hard

Fill both blanks to stop recursion when sum exceeds k and to continue otherwise.

DSA C

int sum = 0;
for (int i = 0; i < combSize; i++) {
    sum += combination[i];
}
if (sum [1] k) {
    return;
} else if (sum [2] k) {
    // continue recursion
}

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A>

B==

C<

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using == to stop causes missing some cases.

Using <= to continue causes infinite loops.

If sum is greater than k, stop recursion. If sum is less than k, continue searching.

5fill in blank

hard

Fill all three blanks to print the current combination correctly.

DSA C

if (sum == k) {
    printf("Combination: ");
    for (int i = 0; i [1] combSize; i++) {
        printf("%d", combination[i]);
        if (i [2] combSize - 1) {
            printf(", ");
        }
    }
    printf("\n");
    return;
}

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A<

B==

C!=

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using == in loop condition causes only one iteration.

Using == for comma check prints comma after last element.

Loop from i < combSize; print comma if i != combSize - 1; use <= for safe boundary checks.