IBM Coding Assessment: Common Questions and Expert Answers

2. Write a program to find the factorial of a number.

Example

Input
5

Output
Factorial of 5 = 120

C

#include <stdio.h>

int main() {
    int n;
    unsigned long long factorial = 1;
    
    printf("Enter a positive integer: ");
    scanf("%d", &n);
    
    for (int i = 1; i <= n; ++i) {
        factorial *= i;
    }
    
    printf("Factorial of %d = %llu\n", n, factorial);
    return 0;
}

3. Given a string of characters followed by their frequency, compress it into a proper format.

Example 

Input 
a3b5c2a2

Output
abc

C

#include <stdio.h>
#include <string.h>

void properCompression(const char *s, char *result) {
    int freq[256] = {0}; // Frequency array for ASCII

    for (int i = 0; s[i] != '\0'; i += 2) {
        char c = s[i];
        int count = s[i + 1] - '0';
        freq[c] += count;
    }

    int index = 0;
    for (char c = 'a'; c <= 'z'; c++) {
        if (freq[c] > 0) {
            result[index++] = c;
        }
    }
    result[index] = '\0';
}

int main() {
    char inputStr[] = "a3b5c2a2";
    char compressedResult[100];
    properCompression(inputStr, compressedResult);
    printf("%s\n", compressedResult);
    return 0;
}

4. Write a program to calculate the sum of digits of a number.

Example

Input
12345

Output 
15

C

#include <stdio.h>

int main() {
    int n, sum = 0;
    printf("Enter a number: ");
    scanf("%d", &n);
    
    while (n > 0) {
        sum += n % 10;
        n /= 10;
    }
    
    printf("Sum of digits: %d\n", sum);
    return 0;
}

5. Write a C program to convert the Decimal to a Binary number

Example

Input
10

Output
Binary of the given number = 1010

C

#include <stdio.h>

int main() {
    int n;
    printf("Enter the number to convert: ");
    scanf("%d", &n);
    
    int binary[32], i = 0;
    while (n > 0) {
        binary[i] = n % 2;
        n = n / 2;
        i++;
    }
    
    printf("Binary of the given number = ");
    for (i = i - 1; i >= 0; i--) {
        printf("%d", binary[i]);
    }
    return 0;
}

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6. What is the output of the following program?

Example

Input
No input is required

Output
10

C

#include <stdio.h>

int main() {
    int a = 5, b = 10, c = 15;
    int *arr[] = {&a, &b, &c};
    printf("%d\n", *arr[1]);
    return 0;
}

7. Given an array of prefix XOR values, reconstruct the original array.

Example

Input
3 5 2 10

Output
Original Array: 3 8 10 2

C

#include <stdio.h>

void findOriginalArray(int pref[], int n, int arr[]) {
    arr[0] = pref[0];
    for (int i = 1; i < n; i++) {
        arr[i] = pref[i] ^ pref[i - 1];
    }
}

int main() {
    int pref[] = {3, 5, 2, 10};
    int n = sizeof(pref) / sizeof(pref[0]);
    int originalArray[4];
    findOriginalArray(pref, n, originalArray);
    
    printf("Original Array: ");
    for (int i = 0; i < n; i++) {
        printf("%d ", originalArray[i]);
    }
    printf("\n");
    return 0;
}

8. Write a program to reverse a given string.

Example

Input
nxtwave

Output
evawtxn

C

#include <stdio.h>
#include <string.h>

int main() {
    char str[100];
    printf("Enter a string: ");
    gets(str);
    
    int n = strlen(str);
    for (int i = n - 1; i >= 0; i--) {
        printf("%c", str[i]);
    }
    printf("\n");
    return 0;
}

9. Write a program to check if a number is prime.

Example

Input
29

Output
Prime

C

#include <stdio.h>

int main() {
    int n, isPrime = 1;
    printf("Enter a number: ");
    scanf("%d", &n);
    
    if (n <= 1) isPrime = 0;
    for (int i = 2; i * i <= n; i++) {
        if (n % i == 0) {
            isPrime = 0;
            break;
        }
    }
    
    if (isPrime) printf("Prime\n");
    else printf("Not Prime\n");
    return 0;
}

10. Write a program to count the number of vowels in a given string

Input
Hello World

Output
Number of vowels: 3

C

#include <stdio.h>

int main() {
    char str[100];
    int count = 0;
    
    printf("Enter a string: ");
    gets(str);
    
    for (int i = 0; str[i] != '\0'; i++) {
        char ch = str[i];
        if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u' ||
            ch == 'A' || ch == 'E' || ch == 'I' || ch == 'O' || ch == 'U') {
            count++;
        }
    }
    
    printf("Number of vowels: %d\n", count);
    return 0;
}

To improve your probabilities of succeeding the IBM coding assessment, you can explore research-based strategies and the best online resources or preparation techniques you can employ:

1. Understand the IBM Exam Pattern and Syllabus: Check out the current syllabus for the IBM assessment test and the pattern of the exam. Usually the IBM coding assessment test has 2 coding questions to be done in 55 minutes and can be attempted in languages like C, C++, Java, Python, etc. Therefore, it is essential to know beforehand the question format and the marking scheme for the exams. It would make your IBM online assessments preparation much more productive.

2. Practice on Realistic Coding Platforms: Use platforms such as HackerRank, CodeSignal, LeetCode, and Nxtwave LastMinutePro, which offer IBM placement papers with answers and practice problems that closely resemble actual IBM coding questions. Practicing on these platforms helps you get comfortable with the interface and types of problems you’ll encounter.

3. Master Core Topics from the Syllabus: Focus your preparation on the most frequently tested topics in the IBM coding assessment syllabus, such as arrays, strings, recursion, sorting algorithms, data structures (stacks, queues, trees, graphs), and mathematical problems. Familiarity with these areas is essential for IBM online exam preparation.

4. Write Efficient and Clean Code: IBM values not just correct solutions, but also code quality and optimization. Always use meaningful variable names, proper indentation, and comments where needed. Be prepared to analyze and discuss the time and space complexity of your solutions, as this is a common follow-up in interviews.

5. Read and Analyze Each Problem Carefully: Take time to fully understand the problem statement, input/output format, and constraints before coding. Misinterpreting the question is a common pitfall in coding assessments.

6. Plan Your Solution Before Coding: Outline your approach, consider possible edge cases, and think through your logic before you start typing code. This minimizes errors and saves time during the actual assessment.

7. Test Your Code with Sample and Edge Cases: When you finish each problem, run your code against sample inputs as well as edge cases (without inputs, large numbers, or edge cases that meet some other unique constraints) to test your robustness.

8. Manage Your Time Effectively: Pay attention to the timer and tend to your time based on the difficulty of each question. If you struggle, move on to the next question and return if you have time. Practicing IBM placement papers, with a slight time restriction and/or timed mock interview can help you build this skill.

9. Simulate Exam Conditions with Mock Interviews: Take mock interviews and timed practice tests to replicate real exam pressure. This builds confidence and helps you stay calm and focused during the actual IBM coding assessment.

10. Leverage Community Resources and Shared Experiences: Find sources to previous IBM placement papers with answers, IBM communication skills assessments, and shared experiences from others who have gone through the interview process in online forums and blogs. All of this can be helpful in framing your expectations and knowing how to prepare.

By utilizing these strategies, in conjunction with Nxtwave LastMinutePro, CodeSignal, HackerRank, and LeetCode for IBM online exam preparation, you will successfully build the confidence and proficiency required for the IBM coding assessment.

As you conclude this guide, keep in mind that the essence of succeeding on an IBM coding assessment is more than solving a handful of problems; it's about the thinking of an engineer. Achieving success in their coding assessments means solving the problems thoughtfully, writing clean and efficient code, and remaining calm under pressure. Being confident in these areas prepares you not only for their assessments, but also to establish a problem-solving mindset that IBM looks for in its engineers.

Here’s what you will walk away with from this blog

1. Clear roadmap of IBM’s coding test — how it’s structured, what’s asked, and how to tackle it smartly.
2. Real coding examples that matter — step-by-step programs in C that mirror IBM’s actual questions.
3. Essential topics decoded — arrays, strings, recursion, and data structures explained simply for fast revision.
4. Proven strategies from top performers — how they managed time, debugged efficiently, and stayed confident.
5. Practical preparation plan — tools, mock platforms, and insider tips to make your IBM attempt count.

Now it’s your turn code, practice, and let your logic do the talking.

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Karthik was able to transform his career from a boring job to an exciting job in software!

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1. How do I prepare for IBM coding and technical rounds?

Practice coding problems on platforms like Hackerrank, review previous year's questions and engage in mock interviews to build confidence and improve your coding skills.

2. What should I do if I get stuck on a problem?

Breakdown the problem into smaller parts, and try to implement a brute force solution first. If that doesn't work, move on to the next question and come back if time permits.

3. What is the format of the IBM coding assessment?

The IBM coding assessment typically consists of 2 coding questions to be solved in 55 minutes. The test is usually non-adaptive and may not include negative marking.

4. Which programming languages are permitted to use for the IBM coding test?

Typically, you can complete the IBM coding test in languages such as C, C++, Java, and Python. Every year or sometimes for every platform, the options may change, so always verify in the instructions on your assessment portal.

5. What is the difficulty level of the IBM coding questions?

The coding questions are ranged between medium and high difficulty level, concentrating on clarity of logic, data structures, and algorithms.

6. What syllabus topics can one expect in the IBM coding assessment?

Common topics include arrays, strings, recursion, sorting algorithms, data structures (stacks, queues, trees, and graphs), and somewhat basic mathematical problems.

7. Is there a separate English or communication skills assessment?

YES, IBM might have a distinct assessment for our English or communication skills - as a part of the overall interview process. The examinations can be verbal ability or written ability in English.

8. How should I prepare for the IBM coding assessment?

Try to practice coding problems on Nxtwave LatMinPro, HackerRank, and LeetCode. Look at previous years' questions, think about doing mock interviews, and focus on understanding the problem statement well.

9. What should I do if I get stuck on a problem during the assessment?

Try to break the problem down into parts, start with brute force, and after that consider the following question if you can't solve the problem, or come back if you have time.

10. Are there resources or sample papers available for practice?

Yes, you can find IBM placement papers and sample questions on platforms like PrepInsta, HackerRank, and company-specific blogs.

11. What is the IBM hiring process after the coding assessment?

After clearing the coding assessment, candidates may face technical interviews, communication/English tests, and HR interviews as part of the selection process.

12. Is there a retake option if I face technical issues during the online test?

Retake policies depend if you are following IBM's recruitment guidelines for that year. If you run into technical issues, please reach out to the support team included in your assessment instructions as soon as possible.

13. What types of coding questions are asked in IBM interviews?

Commonly, candidates face questions related to data structures, algorithms, and general problem-solving.