Coin Change Total Number of Ways in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the ways array with 0.

DSA C

int ways[amount + 1] = {0};
ways[0] = [1];

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A1

B0

Camount

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting ways[0] to 0 will cause the algorithm to fail to count any combinations.

Using negative or amount value instead of 1.

ways[0] = 1 means there is exactly one way to make amount 0: by choosing no coins.

2fill in blank

medium

Complete the code to update the ways array inside the nested loop.

DSA C

for (int i = 0; i < n; i++) {
    for (int j = coins[i]; j <= amount; j++) {
        ways[j] += [1];
    }
}

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Aways[j - coins[i]]

Bcoins[i]

Cj

Dways[j]

Attempts:

3 left

💡 Hint

Common Mistakes

Adding coins[i] directly instead of ways[j - coins[i]].

Using ways[j] on the right side causes incorrect counting.

ways[j] is updated by adding ways[j - coins[i]] which represents the number of ways to make amount j - coins[i].

3fill in blank

hard

Fix the error in the loop condition to avoid out-of-bounds access.

DSA C

for (int j = coins[i]; j [1] amount; j++) {
    ways[j] += ways[j - coins[i]];
}

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A>

B<

C<=

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using < causes the last amount to be skipped.

Using > or >= causes the loop to not run or run incorrectly.

The loop must run while j is less than or equal to amount to cover all amounts up to the target.

4fill in blank

hard

Fill both blanks to complete the function signature and return statement.

DSA C

int [1](int coins[], int n, int amount) {
    int ways[amount + 1] = {0};
    ways[0] = 1;
    for (int i = 0; i < n; i++) {
        for (int j = coins[i]; j <= amount; j++) {
            ways[j] += ways[j - coins[i]];
        }
    }
    return [2];
}

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AcountWays

Bways[amount]

Camount

Dcoins

Attempts:

3 left

💡 Hint

Common Mistakes

Returning amount or coins instead of ways[amount].

Using a wrong function name that does not match the problem.

The function is named countWays and returns ways[amount], the total number of ways to make the amount.

5fill in blank

hard

Fill all three blanks to complete the main function that calls countWays and prints the result.

DSA C

#include <stdio.h>

int countWays(int coins[], int n, int amount);

int main() {
    int coins[] = {1, 2, 5};
    int n = sizeof(coins) / sizeof(coins[0]);
    int amount = 5;
    int result = [1](coins, n, amount);
    printf("Total ways to make %d: %d\n", [2], [3]);
    return 0;
}

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AcountWays

Bamount

Cresult

Dcoins

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names in printf.

Calling a wrong function or passing wrong arguments.

Call countWays with coins, n, amount; print amount and result to show total ways.