Jump Game Problem in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the array length is zero.

DSA C

if ([1] == 0) {
    return 1;
}

Drag options to blanks, or click blank then click option'

Asize

Bnums

Cnums[0]

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using the array name instead of its length.

Checking the first element instead of length.

The variable length holds the size of the array. Checking if it is zero means the array is empty.

2fill in blank

medium

Complete the code to update the maximum reachable index.

DSA C

maxReach = (maxReach > i + nums[i]) ? maxReach : [1];

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Ai + nums[i]

Bnums[i]

CmaxReach + 1

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Using only the jump length without adding the index.

Using maxReach + 1 incorrectly.

We update maxReach to the farthest index reachable from current position i, which is i + nums[i].

3fill in blank

hard

Fix the error in the loop condition to iterate over the array correctly.

DSA C

for (int i = 0; i [1] length; i++) {
    if (i > maxReach) return 0;
    maxReach = (maxReach > i + nums[i]) ? maxReach : i + nums[i];
}

Drag options to blanks, or click blank then click option'

A<=

B<

C>

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using <= causes out-of-bounds access.

Using > or >= causes the loop to never run.

The loop should run while i is less than length to avoid going out of bounds.

4fill in blank

hard

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

DSA C

int canJump([1] nums[], int [2]) {
    int maxReach = 0;
    for (int i = 0; i < length; i++) {
        if (i > maxReach) return 0;
        maxReach = (maxReach > i + nums[i]) ? maxReach : i + nums[i];
    }
    return 1;
}

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Aint

Bsize

Clength

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using bool instead of int for parameters.

Using incorrect parameter names.

The function takes an integer array nums and its length length as parameters.

5fill in blank

hard

Fill all three blanks to complete the main function that tests the jump game.

DSA C

int main() {
    int nums[] = {2, 3, 1, 1, 4};
    int [1] = sizeof(nums) / sizeof(nums[0]);
    int result = canJump(nums, [2]);
    if (result [3] 1) {
        printf("Can reach the end\n");
    } else {
        printf("Cannot reach the end\n");
    }
    return 0;
}

Drag options to blanks, or click blank then click option'

Alength

Bsize

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names for length.

Using != instead of == in the if condition.

We calculate the array length as length, pass it to canJump, and check if the result equals 1.

Practice

1. What is the main goal of the Jump Game problem?

easy

A. Calculate the minimum jump length required to reach the last index

B. Determine if you can reach the last index from the first index by jumping

C. Count the total number of jumps needed to reach the end

D. Find the maximum jump length from the first index

Solution

1. Step 1: Understand the problem statement

   The Jump Game problem asks if it is possible to move from the first index to the last index by jumping forward using the values at each index as maximum jump lengths.

2. Step 2: Identify the goal

   The goal is to check if the last index is reachable, not to count jumps or find maximum jump length.

3. Final Answer:

   Determine if you can reach the last index from the first index by jumping -> Option B

4. Quick Check:

   Goal = Reach last index [OK]

Hint: Focus on reachability, not jump counts or lengths [OK]

Common Mistakes:

• Confusing maximum jump length with reachability
• Trying to count jumps instead of checking possibility
• Assuming jumps can go backward

2. Which of the following is the correct syntax to declare an integer array nums of size 5 in C for the Jump Game problem?

easy

A. int[] nums = new int[5];

B. int nums = [5];

C. int nums(5);

D. int nums[5];

Solution

1. Step 1: Recall C array declaration syntax

   In C, arrays are declared by specifying the type, name, and size in square brackets, like int nums[5];.

2. Step 2: Check each option

   int nums[5]; matches correct C syntax. int nums = [5]; uses invalid assignment. int nums(5); uses parentheses which is incorrect. int[] nums = new int[5]; is Java syntax.

3. Final Answer:

   int nums[5]; -> Option D

4. Quick Check:

   C array syntax = int nums[5]; [OK]

Hint: Use type name[size] for arrays in C [OK]

Common Mistakes:

• Using Java or C++ style array declarations
• Using parentheses instead of square brackets
• Assigning array size with equals sign

3. What will be the output of the following C code snippet for the Jump Game problem?

int nums[] = {2, 3, 1, 1, 4};
int n = 5;
int maxReach = 0;
for (int i = 0; i < n; i++) {
    if (i > maxReach) {
        printf("false\n");
        return 0;
    }
    if (i + nums[i] > maxReach) {
        maxReach = i + nums[i];
    }
}
printf("true\n");

medium

A. true

B. false

C. Compilation error

D. Runtime error

Solution

1. Step 1: Trace the loop and maxReach updates

   Start with maxReach=0. At i=0, maxReach = max(0, 0+2)=2. i=1 ≤ 2, maxReach = max(2,1+3)=4. i=2 ≤ 4, maxReach = max(4,2+1)=4. i=3 ≤ 4, maxReach = max(4,3+1)=4. i=4 ≤ 4, maxReach = max(4,4+4)=8.

2. Step 2: Check if loop completes without returning false

   Since i never exceeds maxReach, loop completes and prints "true".

3. Final Answer:

   true -> Option A

4. Quick Check:

   maxReach covers all indices = true [OK]

Hint: Check if current index exceeds max reachable index [OK]

Common Mistakes:

• Stopping early without updating maxReach
• Confusing index with jump length
• Assuming false if maxReach equals index

4. Identify the bug in the following C code snippet for the Jump Game problem:

int canJump(int* nums, int n) {
    int maxReach = 0;
    for (int i = 0; i <= n; i++) {
        if (i > maxReach) return 0;
        if (i + nums[i] > maxReach) maxReach = i + nums[i];
    }
    return 1;
}

medium

A. Return values should be swapped (1 for false, 0 for true)

B. maxReach should be initialized to -1

C. Loop condition should be i < n, not i <= n

D. nums array should be declared inside the function

Solution

1. Step 1: Analyze the loop condition

   The loop runs from i=0 to i<=n, which means it accesses nums[n], an out-of-bounds index causing undefined behavior.

2. Step 2: Correct the loop condition

   The loop should run while i < n to avoid accessing beyond the array.

3. Final Answer:

   Loop condition should be i < n, not i <= n -> Option C

4. Quick Check:

   Array index in bounds = i < n [OK]

Hint: Loop up to n-1 to avoid out-of-bounds access [OK]

Common Mistakes:

• Using <= instead of < in loop condition
• Ignoring array boundary checks
• Incorrect return values for boolean

5. Given the array nums = {3, 2, 1, 0, 4}, why does the standard greedy Jump Game algorithm return false for reachability?

hard

A. Because index 3 has a jump length of 0, blocking further progress

B. Because the array length is less than 5

C. Because the first element is too large

D. Because the last element is unreachable due to negative jumps

Solution

1. Step 1: Trace jumps from start

   Start at index 0 with jump length 3, maxReach = 3. Indices 1, 2, 3 are reachable. At index 3, jump length is 0, so maxReach stays 3.

2. Step 2: Check if last index is reachable

   Last index is 4, which is beyond maxReach 3, so it is unreachable, causing the algorithm to return false.

3. Final Answer:

   Because index 3 has a jump length of 0, blocking further progress -> Option A

4. Quick Check:

   Zero jump blocks path = false [OK]

Hint: Zero jump at reachable index blocks reaching the end [OK]

Common Mistakes:

• Ignoring zero jump blocking
• Assuming array length affects reachability
• Thinking negative jumps exist in problem