CoCubes Coding Questions 2026: Practice Problems with Solutions

CoCubes coding problems test array manipulation, basic searching, and mathematical logic, not advanced data structures or algorithmic theory.

That distinction matters practically. Students who prepare exclusively with competitive programming platforms often overshoot, spending hours on dynamic programming and graph traversal when the actual CoCubes coding section rewards clean, readable solutions to straightforward problems. The goal is accurate output on all test cases, including edge cases the visible sample input doesn’t cover.

For the full test structure, section timing, and what each section carries in weight, the CoCubes syllabus and test pattern guide covers the platform architecture. This article focuses on the coding section specifically: what problem categories appear, and how to solve them.

CoCubes Coding Section: Structure and What to Expect

CoCubes is now part of the HirePro campus hiring suite. The platform lets companies configure the coding section independently, so the exact setup varies by drive. The standard configuration for most mid-size IT and services company drives looks like this:

Parameter	Typical range
Number of coding problems	1 to 2
Section time	45 to 60 minutes
Languages available	C, C++, Java, Python
Negative marking	None
Test case evaluation	Hidden test cases checked on submission

Two things stay constant across configurations: there is no negative marking, and the evaluation is output-based. Your code runs against a set of test cases (some visible in the problem statement, some hidden). Getting the visible sample right is necessary but not sufficient. The hidden test cases typically check boundary conditions: an empty array, an array with a single element, very large numbers, or duplicate values.

The problem categories below appear across the majority of CoCubes drives at Tier-2 and Tier-3 colleges. They’re ordered roughly by frequency.

Problem category	What it tests
Array traversal and manipulation	Loops, indexing, condition checks
Searching problems	Linear search, pattern-matching in arrays
Mathematical problems	Number properties, digit operations, divisibility
String manipulation	Character traversal, comparisons, reversal

Array and Searching Problems

Array problems make up the highest share of CoCubes coding questions. The three problems below are among the most-repeated templates. Solutions are in C; the logic translates directly to C++, Java, or Python with minor syntax changes.

Count Co-Prime Pairs in an Array

Two numbers are co-prime if their Greatest Common Divisor (GCD) is 1. The Euclidean algorithm computes GCD efficiently by repeatedly replacing the larger number with the remainder when divided by the smaller.

• Problem: Given an array of N integers, count all pairs (arr[i], arr[j]) where i < j and GCD(arr[i], arr[j]) = 1.
• Sample input: N = 3, array = [1, 2, 3]
• Sample output: 3
• Verification: GCD(1,2) = 1 (co-prime), GCD(1,3) = 1 (co-prime), GCD(2,3) = 1 (co-prime). Count = 3. Correct.

#include <stdio.h>

int gcd(int a, int b) {
    while (a != 0) {
        int temp = a;
        a = b % a;
        b = temp;
    }
    return b;
}

int count_coprime_pairs(int arr[], int n) {
    int count = 0;
    for (int i = 0; i < n - 1; i++) {
        for (int j = i + 1; j < n; j++) {
            if (gcd(arr[i], arr[j]) == 1) {
                count++;
            }
        }
    }
    return count;
}

int main() {
    int n;
    scanf("%d", &n);
    int arr[n];
    for (int i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }
    printf("%d", count_coprime_pairs(arr, n));
    return 0;
}

• Edge case to check: an array where every element is the same even number. GCD of any pair equals that number (not 1), so the output should be 0. Test this mentally before submitting.

Find the Nth Occurrence of a Number

• Problem: Given an array, a target value, and an integer N, return the index of the Nth occurrence of the target in the array. Return -1 if fewer than N occurrences exist.
• Sample input: Array = [1, 4, 6, 7, 6, 3, 6], target = 6, N = 3
• Sample output: 6
• Verification: Index 2 has 6 (1st), index 4 has 6 (2nd), index 6 has 6 (3rd). Return index 6. Correct.

#include <stdio.h>

int main() {
    int arr[100], i, n, num, occurrence, count = 0;
    scanf("%d", &n);
    for (i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }
    scanf("%d %d", &num, &occurrence);
    for (i = 0; i < n; i++) {
        if (arr[i] == num) {
            count++;
            if (count == occurrence) {
                printf("%d", i);
                return 0;
            }
        }
    }
    printf("-1");
    return 0;
}

• Edge case to check: N = 0 or a negative N. The problem statement usually guarantees N >= 1, but verify with the sample input format. If N = 0 is possible, the output is typically -1 or 0 depending on the definition.

Find the Second Largest Element

• Problem: Given an array of N integers, find the second largest distinct value.
• Sample input: N = 7, array = [23, 45, 7, 34, 25, 25, 89]
• Sample output: 45
• Verification: Largest = 89, Second largest = 45. Correct.

#include <stdio.h>

int main() {
    int n, i, first, second;
    scanf("%d", &n);
    int arr[n];
    for (i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }
    first = second = -1;
    for (i = 0; i < n; i++) {
        if (arr[i] > first) {
            second = first;
            first = arr[i];
        } else if (arr[i] > second && arr[i] != first) {
            second = arr[i];
        }
    }
    printf("%d", second);
    return 0;
}

• Edge case to check: an array where all elements are identical (e.g., [5, 5, 5]). The code above returns -1 in that case; confirm whether -1 is the expected output or whether the problem expects a different sentinel value.

Mathematical and Logic Problems

Number properties (digit sums, Armstrong numbers, divisibility) appear frequently as the second or third problem in a CoCubes coding section. They’re typically shorter to code than array problems but require careful handling of the loop termination condition.

Sum of Digits

• Problem: Given a non-negative integer, compute the sum of its digits.
• Sample input: 456
• Sample output: 15
• Verification: 4 + 5 + 6 = 15. Correct.

#include <stdio.h>

int main() {
    int n, sum = 0;
    scanf("%d", &n);
    while (n > 0) {
        sum += n % 10;
        n /= 10;
    }
    printf("%d", sum);
    return 0;
}

• Edge case to check: n = 0. The while loop never executes, sum stays 0. That is the correct answer for digit sum of 0.

Check Armstrong Number

A 3-digit Armstrong number equals the sum of the cubes of its digits. 153 is an Armstrong number because 1 cubed + 5 cubed + 3 cubed = 1 + 125 + 27 = 153.

• Problem: Given a positive integer, determine whether it is a 3-digit Armstrong number.
• Sample input: 153
• Sample output: Armstrong
• Verification: 1 + 125 + 27 = 153. Matches input. Correct.

#include <stdio.h>

int main() {
    int n, original, digit, sum = 0;
    scanf("%d", &n);
    original = n;
    while (n > 0) {
        digit = n % 10;
        sum += digit * digit * digit;
        n /= 10;
    }
    if (sum == original) {
        printf("Armstrong");
    } else {
        printf("Not Armstrong");
    }
    return 0;
}

String Manipulation Problems

String problems in CoCubes typically involve character-level traversal: reversals, palindrome checks, and character frequency counts. The logic is straightforward; the common error is off-by-one indexing when working with C character arrays.

Palindrome Check

• Problem: Given a string, determine whether it reads the same forwards and backwards.
• Sample input: racecar
• Sample output: Palindrome
• Verification: racecar reversed = racecar. Palindrome. Correct.

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

int main() {
    char str[100];
    scanf("%s", str);
    int n = strlen(str);
    int is_palindrome = 1;
    for (int i = 0; i < n / 2; i++) {
        if (str[i] != str[n - 1 - i]) {
            is_palindrome = 0;
            break;
        }
    }
    printf("%s", is_palindrome ? "Palindrome" : "Not Palindrome");
    return 0;
}

• Edge case to check: single-character strings (always a palindrome), empty strings (check whether the problem guarantees non-empty input), and strings with mixed case (“Racecar” vs “racecar”). If case-insensitive comparison is required, convert to lowercase before checking.

Count Vowels in a String

• Problem: Given a string, count the number of vowel characters (a, e, i, o, u, both upper and lower case).
• Sample input: Hello World
• Sample output: 3
• Verification: e, o, o are the vowels in “Hello World”. Count = 3. Correct.

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

int main() {
    char str[200];
    fgets(str, sizeof(str), stdin);
    int count = 0;
    for (int i = 0; str[i] != '\0'; i++) {
        char c = tolower(str[i]);
        if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u') {
            count++;
        }
    }
    printf("%d", count);
    return 0;
}

• Edge case to check: strings with no vowels (output: 0), strings with only vowels, and strings with spaces or punctuation. The tolower conversion handles upper-case vowels cleanly.

Preparing for the CoCubes Coding Section

A few practices separate candidates who clear the coding section from those who stall on hidden test cases.

Read the full problem statement first, then look at sample input. The problem statement carries the edge case definitions: what to do when the array is empty, whether the target value can appear zero times, whether numbers can be negative. Students who jump to the sample input without reading the full specification tend to build solutions that fail on hidden test cases.

Trace your solution manually with the sample input before submitting. The co-prime pair count, the Nth occurrence index, the digit sum: each solution above can be traced in under two minutes with a pencil on paper. That two-minute check catches most off-by-one errors and loop boundary mistakes.

Pair coding prep with aptitude prep. CoCubes drives run the aptitude and coding sections in sequence. A strong aptitude score doesn’t rescue a blank coding section, and a complete coding solution doesn’t offset a poor aptitude result. The CoCubes aptitude questions practice set and CoCubes logical reasoning practice cover the non-coding sections in the same structured format.

Handle edge cases before looking elegant. A solution that returns correct output for the sample input and three common edge cases (empty input, single element, all-identical elements) scores higher than a cleaner solution that breaks on one of them. Use every minute of remaining time to test boundary conditions, not to refactor working code.

The problem-decomposition discipline running through every question above (define the input, identify the condition to check, verify the sample, then test boundaries) is the same reasoning skill that makes prompt engineering productive. The co-prime problem uses GCD as a composable building block; reliable LLM prompts work the same way, chaining well-defined sub-steps. TinkerLLM at ₹299 is the entry point if you want to apply that structured reasoning to working with language model APIs once your placement prep is done.