Top 30 Infosys Coding Interview Questions and Answers

December 16, 2024January 10, 2025 Shailja Kaushik

Infosys is one of the leading IT services companies globally and is renowned for its rigorous recruitment process, especially in coding and technical rounds. With over 300,000 employees across 50+ countries, Infosys emphasizes problem-solving skills and programming expertise when selecting candidates. The coding questions in their hiring process test logical reasoning, data structures, algorithms, and real-world problem-solving abilities. In this blog, we will discuss some of the commonly asked Infosys coding interview questions and answers and provide insightful answers to help you ace your interview.

Table of Contents

Infosys Coding Interview Questions and Answers For Freshers

When preparing for an entry-level job position at Infosys, one of the key components of the interview process involves coding assessments. These assessments are designed to evaluate your problem-solving skills, understanding of algorithms, and coding proficiency. Below are Infosys coding interview questions and answers for freshers.

Q1. What will be the output of the Pseudo Code provided below?

#include <stdio.h>
int main()
{
    float i;
    i = 1;
    printf("%f", i);
    return 0;
}

Sample Answer: The given C code involves printing a floating-point value. The output of the provided C pseudo code will be:

1.000000

Explanation:

The variable i is declared as a float and initialized with the value 1.
The printf function is used to print the value of i. The format specifier %f is used, which is for printing floating-point numbers in C.
In C, when a float is printed using %f, it prints the number with six digits after the decimal point by default.

So, when the value 1 is printed as a floating-point number, it is displayed as 1.000000 (with six decimal places). If you want to modify the precision of the printed number, you could adjust the format specifier (e.g., %.2f for two decimal places).

Q2. Write a C program to arrange the given number to form the biggest number.

Sample Answer: In this task, we need to write a C program that arranges a given set of numbers to form the largest possible number when concatenated. To achieve this, we treat the numbers as strings, allowing us to compare their concatenated versions in different orders. We will sort the numbers based on this comparison, ensuring that the resulting concatenation produces the largest number. The program will then print the largest number formed by the sorted input. Here’s a C program to implement this solution:

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

// Comparison function to compare two strings based on concatenation
int compare(const void *a, const void *b) {
    // Convert the pointers to strings
    char *str1 = *(char **)a;
    char *str2 = *(char **)b;

    // Compare concatenated strings in both orders
    if (strcmp(str1, str2) > 0) return -1;
    if (strcmp(str1, str2) < 0) return 1;
    return 0;
}

int main() {
    int n;

    // Read the number of elements
    printf("Enter the number of elements: ");
    scanf("%d", &n);

    // Create an array of strings to store the numbers
    char *arr[n];

    // Read the input numbers as strings
    printf("Enter the numbers: \n");
    for (int i = 0; i < n; i++) {
        arr[i] = (char *)malloc(20 * sizeof(char)); // Allocate memory for each string
        scanf("%s", arr[i]);
    }

    // Sort the array using qsort and the custom comparison function
    qsort(arr, n, sizeof(char *), compare);

    // Print the largest number formed
    printf("The largest number formed is: ");
    for (int i = 0; i < n; i++) {
        printf("%s", arr[i]);
    }

    // Free allocated memory
    for (int i = 0; i < n; i++) {
        free(arr[i]);
    }

    return 0;
}

Explanation:

Input: The program first takes the number of elements (n) and then takes n numbers as strings. This is necessary because numbers could have different lengths, and we want to treat them as strings for concatenation.
Sorting: The program sorts the strings based on how they compare when concatenated in both possible orders. For example, for two numbers “34” and “3”, it compares “343” and “334”. It chooses the order that forms the larger concatenated string.
Output: After sorting the strings, the program concatenates and prints them to form the largest possible number.
Memory Management: Memory is dynamically allocated for the strings and freed at the end.

Q3. How do you rotate a matrix by 90 degrees? Write a C program for this.

Sample Answer: To rotate a matrix by 90 degrees clockwise, you can follow these steps:

Transpose the matrix: Swap the rows and columns of the matrix.
Reverse the rows: After transposing, reverse each row to get the final rotated matrix.

#include <stdio.h>

#define N 3 // Define the size of the matrix (NxN)

// Function to print the matrix
void printMatrix(int matrix[N][N]) {
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }
}

// Function to rotate the matrix by 90 degrees clockwise
void rotateMatrix(int matrix[N][N]) {
    // Step 1: Transpose the matrix
    for (int i = 0; i < N; i++) {
        for (int j = i; j < N; j++) {
            // Swap matrix[i][j] with matrix[j][i]
            int temp = matrix[i][j];
            matrix[i][j] = matrix[j][i];
            matrix[j][i] = temp;
        }
    }

    // Step 2: Reverse each row
    for (int i = 0; i < N; i++) {
        int start = 0, end = N - 1;
        while (start < end) {
            // Swap elements in the row
            int temp = matrix[i][start];
            matrix[i][start] = matrix[i][end];
            matrix[i][end] = temp;
            start++;
            end--;
        }
    }
}

int main() {
    // Initialize a matrix
    int matrix[N][N] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };

    printf("Original Matrix:\n");
    printMatrix(matrix);

    // Rotate the matrix by 90 degrees
    rotateMatrix(matrix);

    printf("\nMatrix after rotating 90 degrees clockwise:\n");
    printMatrix(matrix);

    return 0;
}

Also Read: Infosys Interview Questions

Q4. How do you find the missing characters to make a string pangram using a C program?

Sample Answer: To answer the coding questions asked in Infosys interview, you need to check if each letter of the alphabet (from ‘a’ to ‘z’) is present in the string. If any letter is missing, you can add it to a list of missing characters. Here is the code to implement this:

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

#define ALPHABET_SIZE 26

// Function to find missing characters for a pangram
void findMissingCharacters(char str[]) {
    // Create an array to keep track of letters present in the string
    int present[ALPHABET_SIZE] = {0};

    // Iterate over each character in the string
    for (int i = 0; str[i] != '\0'; i++) {
        // Convert the character to lowercase
        char ch = tolower(str[i]);

        // If the character is a letter, mark it as present
        if (ch >= 'a' && ch <= 'z') {
            present[ch - 'a'] = 1;
        }
    }

    // Print the missing characters
    printf("Missing characters to make the string a pangram: ");
    int foundMissing = 0;
    for (int i = 0; i < ALPHABET_SIZE; i++) {
        if (present[i] == 0) {
            printf("%c ", 'a' + i);
            foundMissing = 1;
        }
    }

    // If no missing characters, the string is already a pangram
    if (!foundMissing) {
        printf("None. The string is already a pangram.");
    }
    printf("\n");
}

int main() {
    char str[1000];

    // Read input string
    printf("Enter a string: ");
    fgets(str, sizeof(str), stdin);

    // Find missing characters to make the string a pangram
    findMissingCharacters(str);

    return 0;
}

Q5. How do you find the number of unique numbers in a given string? Write a C program for this.

Sample Answer: To find the number of unique numbers in a given string, you need to extract all the numbers from the string and track which ones have already appeared. This can be done by using a data structure like a set (or an array, but a set is more efficient. This is the code:

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

#define MAX_NUMBERS 1000 // Define a maximum size for the set of unique numbers

// Function to extract and count unique numbers in the string
int countUniqueNumbers(char str[]) {
    int uniqueNumbers[MAX_NUMBERS];
    int uniqueCount = 0;

    // Initialize all entries in uniqueNumbers to -1 (indicating no number is stored)
    for (int i = 0; i < MAX_NUMBERS; i++) {
        uniqueNumbers[i] = -1;
    }

    char currentNum[20];  // Buffer to store current number (string format)
    int currentIndex = 0;

    // Iterate over the string
    for (int i = 0; i <= strlen(str); i++) {
        if (isdigit(str[i])) {
            // Build the number string
            currentNum[currentIndex++] = str[i];
        } else {
            // If currentNum is not empty and we've reached a non-digit
            if (currentIndex > 0) {
                currentNum[currentIndex] = '\0';  // Null-terminate the current number
                int num = atoi(currentNum);  // Convert the string to an integer

                // Check if the number is already in the uniqueNumbers array
                int isUnique = 1;
                for (int j = 0; j < uniqueCount; j++) {
                    if (uniqueNumbers[j] == num) {
                        isUnique = 0;  // Number is already seen
                        break;
                    }
                }

                // If the number is unique, add it to the uniqueNumbers array
                if (isUnique) {
                    uniqueNumbers[uniqueCount++] = num;
                }

                // Reset currentNum to start building the next number
                currentIndex = 0;
            }
        }
    }

    return uniqueCount;  // Return the count of unique numbers
}

int main() {
    char str[1000];

    // Read the input string
    printf("Enter a string: ");
    fgets(str, sizeof(str), stdin);

    // Count the unique numbers in the string
    int result = countUniqueNumbers(str);

    // Output the result
    printf("Number of unique numbers: %d\n", result);

    return 0;
}

Q6. Write a program for the Subtraction of two Matrices.

Sample Answer: To perform the subtraction of two matrices, you need to subtract the corresponding elements of the two matrices. If both matrices are of the same size, matrix subtraction is straightforward.

#include <stdio.h>

#define MAX_ROWS 10
#define MAX_COLS 10

// Function to subtract two matrices
void subtractMatrices(int matrix1[MAX_ROWS][MAX_COLS], int matrix2[MAX_ROWS][MAX_COLS], int result[MAX_ROWS][MAX_COLS], int rows, int cols) {
    // Iterate over each element and subtract corresponding elements
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            result[i][j] = matrix1[i][j] - matrix2[i][j];
        }
    }
}

// Function to print a matrix
void printMatrix(int matrix[MAX_ROWS][MAX_COLS], int rows, int cols) {
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }
}

int main() {
    int matrix1[MAX_ROWS][MAX_COLS], matrix2[MAX_ROWS][MAX_COLS], result[MAX_ROWS][MAX_COLS];
    int rows, cols;

    // Input the dimensions of the matrices
    printf("Enter the number of rows and columns: ");
    scanf("%d %d", &rows, &cols);

    // Input the first matrix
    printf("Enter the elements of the first matrix:\n");
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            scanf("%d", &matrix1[i][j]);
        }
    }

    // Input the second matrix
    printf("Enter the elements of the second matrix:\n");
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            scanf("%d", &matrix2[i][j]);
        }
    }

    // Perform matrix subtraction
    subtractMatrices(matrix1, matrix2, result, rows, cols);

    // Output the result
    printf("\nResult of matrix subtraction:\n");
    printMatrix(result, rows, cols);

    return 0;
}

Q7. How do you multiply two matrices and show results through another matrix? Write a C program.

Sample Answer: Matrix multiplication involves multiplying rows of the first matrix with columns of the second matrix, and summing up the products of the corresponding elements. The result of the multiplication will be a new matrix. Here is the code:

#include <stdio.h>

#define MAX_ROWS 10
#define MAX_COLS 10

// Function to multiply two matrices
void multiplyMatrices(int matrix1[MAX_ROWS][MAX_COLS], int matrix2[MAX_ROWS][MAX_COLS], int result[MAX_ROWS][MAX_COLS], int rows1, int cols1, int rows2, int cols2) {
    // Initialize the result matrix to 0
    for (int i = 0; i < rows1; i++) {
        for (int j = 0; j < cols2; j++) {
            result[i][j] = 0;
        }
    }

    // Perform matrix multiplication
    for (int i = 0; i < rows1; i++) {
        for (int j = 0; j < cols2; j++) {
            for (int k = 0; k < cols1; k++) {
                result[i][j] += matrix1[i][k] * matrix2[k][j];
            }
        }
    }
}

// Function to print a matrix
void printMatrix(int matrix[MAX_ROWS][MAX_COLS], int rows, int cols) {
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }
}

int main() {
    int matrix1[MAX_ROWS][MAX_COLS], matrix2[MAX_ROWS][MAX_COLS], result[MAX_ROWS][MAX_COLS];
    int rows1, cols1, rows2, cols2;

    // Input dimensions and elements of the first matrix
    printf("Enter the number of rows and columns for the first matrix: ");
    scanf("%d %d", &rows1, &cols1);
    printf("Enter the elements of the first matrix:\n");
    for (int i = 0; i < rows1; i++) {
        for (int j = 0; j < cols1; j++) {
            scanf("%d", &matrix1[i][j]);
        }
    }

    // Input dimensions and elements of the second matrix
    printf("Enter the number of rows and columns for the second matrix: ");
    scanf("%d %d", &rows2, &cols2);
    
    // Check if multiplication is possible (cols1 of matrix1 must equal rows2 of matrix2)
    if (cols1 != rows2) {
        printf("Matrix multiplication not possible. The number of columns in the first matrix must be equal to the number of rows in the second matrix.\n");
        return 1;  // Exit the program
    }

    printf("Enter the elements of the second matrix:\n");
    for (int i = 0; i < rows2; i++) {
        for (int j = 0; j < cols2; j++) {
            scanf("%d", &matrix2[i][j]);
        }
    }

    // Perform matrix multiplication
    multiplyMatrices(matrix1, matrix2, result, rows1, cols1, rows2, cols2);

    // Output the result
    printf("\nResult of matrix multiplication:\n");
    printMatrix(result, rows1, cols2);

    return 0;
}

Q8. How do you convert decimal numbers to binary numbers? Write a C Program.

Sample Answer: To convert a decimal number to binary, you can repeatedly divide the number by 2 and record the remainder for each division. This method generates the binary digits (bits) in reverse order, so you’ll need to reverse the remainder at the end to get the correct binary representation. Here is the code:

#include <stdio.h>

void decimalToBinary(int n) {
    // Array to store binary number
    int binary[32];
    
    // Index for binary array
    int i = 0;

    // If n is 0, the binary representation is 0
    if (n == 0) {
        printf("0");
        return;
    }

    // Generate binary number
    while (n > 0) {
        binary[i] = n % 2; // Store remainder in the binary array
        n = n / 2; // Divide number by 2
        i++;
    }

    // Print binary number in reverse order
    printf("Binary: ");
    for (int j = i - 1; j >= 0; j--) {
        printf("%d", binary[j]);
    }
    printf("\n");
}

int main() {
    int num;

    // Input the decimal number
    printf("Enter a decimal number: ");
    scanf("%d", &num);

    // Convert and display the binary equivalent
    decimalToBinary(num);

    return 0;
}

Q9. Write a program in C++ to swap two arrays quickly.

Sample Answer: To swap two arrays in C++, you can use a temporary array to store one array’s values while copying the other array’s values to the first one. However, to do it quickly without needing extra space (except for a constant amount), you can swap the elements of the arrays in place using a simple loop. Here’s a program that demonstrates how to swap two arrays in C++:

#include <iostream>
using namespace std;

// Function to swap two arrays
void swapArrays(int arr1[], int arr2[], int size) {
    for (int i = 0; i < size; i++) {
        // Swap elements of arr1 and arr2
        int temp = arr1[i];
        arr1[i] = arr2[i];
        arr2[i] = temp;
    }
}

// Function to print an array
void printArray(int arr[], int size) {
    for (int i = 0; i < size; i++) {
        cout << arr[i] << " ";
    }
    cout << endl;
}

int main() {
    int size;

    // Input the size of the arrays
    cout << "Enter the size of the arrays: ";
    cin >> size;

    int arr1[size], arr2[size];

    // Input elements for the first array
    cout << "Enter elements for the first array: ";
    for (int i = 0; i < size; i++) {
        cin >> arr1[i];
    }

    // Input elements for the second array
    cout << "Enter elements for the second array: ";
    for (int i = 0; i < size; i++) {
        cin >> arr2[i];
    }

    // Display the original arrays
    cout << "\nOriginal arrays:" << endl;
    cout << "Array 1: ";
    printArray(arr1, size);
    cout << "Array 2: ";
    printArray(arr2, size);

    // Swap the arrays
    swapArrays(arr1, arr2, size);

    // Display the arrays after swapping
    cout << "\nArrays after swapping:" << endl;
    cout << "Array 1: ";
    printArray(arr1, size);
    cout << "Array 2: ";
    printArray(arr2, size);

    return 0;
}

Q10. Write a C++ program to find the area of the incircle of a right-angle triangle.

Sample Answer: To find the area of the incircle of a right-angled triangle, we first need to understand the formula for the radius of the incircle.

Formula to find the radius of the incircle of a right-angled triangle:

For a right-angled triangle with sides aaa, bbb, and hypotenuse ccc, the radius rrr of the incircle can be calculated using the formula:

r=a+b−c2r = \frac{a + b – c}{2}r=2a+b−c

Once we have the radius rrr, the area of the incircle can be found using the formula for the area of a circle:

Area of Incircle=πr2\text{Area of Incircle} = \pi r^2Area of Incircle=πr2

Here is a C++ program to calculate the area of the encircle:

#include <iostream>
#include <cmath> // For using sqrt and M_PI
using namespace std;

// Function to calculate the area of the incircle of a right-angled triangle
double calculateIncircleArea(double a, double b, double c) {
    // Calculate the radius of the incircle
    double r = (a + b - c) / 2.0;

    // Calculate and return the area of the incircle
    return M_PI * r * r; // M_PI is a constant for Pi
}

int main() {
    double a, b, c;

    // Input sides of the right-angled triangle
    cout << "Enter the lengths of the two perpendicular sides (a and b): ";
    cin >> a >> b;

    // Calculate the length of the hypotenuse using the Pythagorean theorem
    c = sqrt(a * a + b * b);

    // Calculate and display the area of the incircle
    double area = calculateIncircleArea(a, b, c);
    cout << "The area of the incircle is: " << area << endl;

    return 0;
}

Pro Tip: Check out our recommended course on how to ace coding interviews to further enhance your skills and prepare like a pro.

Infosys Coding Interview Questions and Answers For Mid-level Candidates

Preparing for a coding interview at Infosys requires a solid understanding of problem-solving skills and technical expertise. Mid-level candidates are often tested on their ability to handle complex coding scenarios, optimize solutions, and apply industry-standard practices. Below are Infosys coding interview questions and answers for mid-level candidates.

Q11. Write a C++ program that converts the given temperature of Fahrenheit into Celsius.

Sample Answer: In this task, we will write a C++ program that converts a given temperature from Fahrenheit to Celsius. The program will prompt the user to input the temperature in Fahrenheit, and then it will apply the formula for conversion. Celsius = (5/9) * (Fahrenheit – 32). The result will be displayed in Celsius after the conversion. Here is the code to implement this solution:

#include <iostream>
using namespace std;

// Function to convert Fahrenheit to Celsius
double fahrenheitToCelsius(double fahrenheit) {
    return (5.0 / 9.0) * (fahrenheit - 32);
}

int main() {
    double fahrenheit;

    // Input the temperature in Fahrenheit
    cout << "Enter temperature in Fahrenheit: ";
    cin >> fahrenheit;

    // Convert Fahrenheit to Celsius
    double celsius = fahrenheitToCelsius(fahrenheit);

    // Output the temperature in Celsius
    cout << fahrenheit << " Fahrenheit is equal to " << celsius << " Celsius." << endl;

    return 0;
}

Also Read: Infosys Java Developer Interview Questions

Q12. Write a Python program to find the sum of all the prime numbers between 1 and N.

Sample Answer: In this task, we will write a Python program that calculates the sum of all prime numbers between 1 and a given number N. The program will first define a function to check whether a number is prime, then iterate through all numbers from 2 to N, summing those that are prime. Finally, the program will output the total sum of the prime numbers in the specified range. Here is the code to implement this solution:

# Function to check if a number is prime
def is_prime(num):
    if num <= 1:
        return False
    for i in range(2, int(num ** 0.5) + 1):
        if num % i == 0:
            return False
    return True

# Function to calculate the sum of all prime numbers between 1 and N
def sum_of_primes(N):
    total = 0
    for num in range(2, N + 1):
        if is_prime(num):
            total += num
    return total

# Main function
if __name__ == "__main__":
    N = int(input("Enter the value of N: "))
    result = sum_of_primes(N)
    print(f"The sum of all prime numbers between 1 and {N} is: {result}")

Q13. Write a Python program to make the largest number from the digits of the array.

Sample Answer: In this task, we will write a Python program that creates the largest number possible from the digits of an array. The program will first convert the elements of the array into strings. Then, it will sort the array in descending order, using a custom sorting technique to ensure that the concatenation of the numbers produces the largest possible number. Finally, the program will join the sorted digits and print the largest number formed.