Top 20 programming questions
Table of Contents
1. Reverse a String without Slicing Operator or Inbuilt Function
Approach:
- The string is converted into a list of characters. Use a loop, which starts from the beginning and end of this list of characters, and swap those characters moving towards the center. Finally this list is converted back into a string.
2. Swap Two Variables With and Without Using Third Variable
Approach:
- Store the value of the first variable in a temporary variable.
Assign the value of the second variable to the first variable. Assign the value of the temporary variable to the second variable. - Without Third Variable:
Either arithmetic operations addition and subtraction or bitwise XOR may be used to swap the values.
3. Approach to Check if a Vowel is Present in a String
Approach:
- Iterate through each character of the string. Check whether the character is a vowel (a, e, i, o, u, A, E, I, O, U).
4. Print Fibonacci Series Using Recursion
Approach:
- Define a recursive function returning the nth Fibonacci number. Base cases for this function are the 0th and 1st Fibonacci numbers.
- The recursive case is the sum of the (n-1)th and the (n-2)th Fibonacci numbers.
5. Check If a String Is a Palindrome
Approach:
- Compare it with its reverse. If they are the same, the string is a palindrome.
6. Check if an Integer is a Palindrome
Approach:
- Convert it to a string.
- Check whether the string is a palindrome using the string palindrome approach.
- Or else, use while loop with modulus operator to to get each digit and reverse it and remaining process is same.
7. Array Sorting in Ascending and Descending Order
Approach:
- The sorting algorithms for the array would be bubble sort, selection sort, or quicksort.
- In ascending order, arrange the elements in such a a way that the smallest element comes first followed by the next smallest element till the largest element.
- In descending order, arrange the elements in such a way that the largest element comes first followed by the next largest element till the smallest element.
8. Factorial of a number
Approach:
- The approach would be to define a function that calculates the factorial, either by loop iteration or recursively. The numbers from 1 through N would be multiplied against each other.
9. Remove All Duplicates from a String
Approach:
- Keep track of the characters that already appeared in a set.
- Traverse a string and build a new one with unique characters.
10. Check Whether the Given Number is Prime
Approach:
- The number is less than 2; hence, it’s not a prime.
- Check for factors from 2 up to the square root of the number.
- If no factors are found, then it’s a prime number.
11. Reverse the Number
Approach:
- Turn the number into a string.
- Reverse the string and then again convert it into a number.
12. Count Number of Digits in an Integer
Approach:
- Firstly, convert the number into a string and then count the characters.
- Secondly, Use a loop to count the number of division by 10.
13. Remove All Duplicates from a List
Approach:
- Using a set, record the unique element.
- Iterating through the list to build another list with unique elements.
14. Check Whether the Given Number is Armstrong
Approach:
- Calculate the number of digits in the number.
- Raise each digit to the power of the number of digits and sum them.
- If the sum equals the original number, it is an Armstrong number.
15. Find the Sum of Squares of Digits of a Number
Approach:
- Convert the number into a string to traverse each digit.
- Take each digit back as an integer, square it, and finally sum the squares.
16. Reverse Each Word in a Given String
Approach:
- Split the string into words.
- Reverse each word individually.
- Join the reversed words back into a string.
17. Star Pattern Problems
Approach:
- Left Aligned: A problem that requires one to print stars in nested loops, with every line containing an increasing number of stars.
- Right Aligned: First print spaces and then stars.
- Pyramid: Spaces and stars have to be printed in such a pattern that it forms a pyramid.
18. Find Number of Occurrences of a Character in a String
Approach:
- Use a loop to traverse the string and count the occurrence of the character.
19. Whether the String is an Anagram
Approach:
- The approach is, sort both strings and compare them.
- Alternatively count the frequency of each character in both strings and compare counts.
20. Whether the String is a Pangram
Approach:
- The approach is to make sure all the letters of the alphabet are included in the string at least once.
- Observe the occurrence of every letter in a set and check whether it contains 26 letters or not.
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