C Programming - Challenges: Exercises, Practice, Solution
This resource offers a total of 175 C Challenges problems for practice. It includes 35 main exercises, each accompanied by solutions, detailed explanations, and four related problems.
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1. Two-Sum Indices Variants
Write a C program to get the indices of two numbers in a given array of integers. This will enable you to get the sum of two numbers equal to a specific target.
Expected Output:
Original Array: 4 2 1 5 Target Value: 7 Indices of the two numbers whose sum equal to target value: 7 1 3
2. Longest Substring Without Repeating Characters Variants
Write a C program to find the length of the longest substring of a given string without repeating characters.
Expected Output:
Original String: xyzxyzyy Length of the longest substring without repeating characters: 3
3. Median of Two Sorted Arrays Variants
Write a C program to find the median of the two given sorted arrays which are not empty.
Expected Output:
Median of the above two sorted arrays is: 10.000000
4. Longest Palindromic Substring Variants
Write a C program to find the longest palindromic substring of a given string. Maximum length of the given string is 1000.
Expected Output:
Original String: yxypxst Longest palindromic substring of the said string: yxy
5. Reverse 32-bit Signed Integer Variants
Write a C program to reverse the digits of a 32-bit signed integer.
Expected Output:
Original integer: 123 Reverse integer : 321
6. Integer to Roman Numeral Variants
Write a C program to convert a given integer to a Roman number.
Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M. Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000Expected Output:
Original integer: 12 Roman number of the said integer: XII
7. Roman Numeral to Integer Variants
Write a C program to convert a Roman number to an integer.
Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M. Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000Expected Output:
Original Roman number: XIV Roman to integer: 14
8. Distinct Triplets Summing to Zero Variants
Write a C program to find all distinct triplets in a given array of integers whose sum is equal to zero.
Expected Output:
Original Array: -2 0 0 1 1 Unique triplets of the said array whose sum equal to zero: -2 1 1
9. Distinct Quadruplets Sum Variants
Write a C program to find all distinct quadruplets in a given array of integers whose sum is equal to zero.
Expected Output:
Original Array: 0 4 7 0 1 6 6 -3 Unique quadruplets of the said array whose sum equal to 12: 0 0 6 6 0 1 4 7
10. Valid Parentheses String Check Variants
Write a C program to check if a given string is valid or not. The string contains the characters '(', ')', '{', '}', '[' and ']'. The string is valid if the open brackets must be closed with the same type of bracket and in the correct order.
Expected Output:
false
11. Generate Well-Formed Parentheses Variants
Write a C program to generate all combinations of well-formed parentheses from n given pairs of parentheses.
Example: Input n = 5 Output: (()())(()) (()())()() (())((())) ..... (())(())() (())()(()) (())()()()
Expected Output:
((((())))) (((()()))) (((())())) (((()))()) (((())))() ((()(()))) ((()()())) ((()())()) ((()()))() ((())(())) ((())()()) ((())())() ((()))(()) ((()))()() (()((()))) (()(()())) (()(())()) (()(()))() (()()(())) (()()()()) (()()())() (()())(()) (()())()() (())((())) (())(()()) (())(())() (())()(()) (())()()() ()(((()))) ()((()())) ()((())()) ()((()))() ()(()(())) ()(()()()) ()(()())() ()(())(()) ()(())()() ()()((())) ()()(()()) ()()(())() ()()()(()) ()()()()()
12. Remove Duplicates from Sorted Array Variants
Write a C program to remove duplicates from a given array of integers..
Expected Output:
Original array: 1 1 2 3 4 4 5 6 6 6 After removing duplicates from the above sorted array: 1 2 3 4 5 6
13. Remove Instances of a Given Value Variants
Write a C program to remove all instances of a given value from a given array of integers and return the length of the updated array.
Expected Output:
Original array: 1 1 2 3 4 4 5 6 6 6 Size of the new array after removing the value 4: 8
14. Find First Occurrence of Substring Variants
Write a C program to find the index of the first occurrence of a given string within another given string. If not found return -1.
Expected Output:
Main string: w3resource.com Substring searched in main string: source Starting position of the substring in the main string: 4
15. Divide Integers Without Multiplication/Division/Mod Variants
Write a C program to divide two given integers without using the multiplication, division and mod operator. Return the quotient after dividing.
Expected Output:
Quotient after dividing 15 and 3 : 5
16. Longest Valid Parentheses Substring Variants
Write a C program to find the length of the longest valid (correct-formed) parentheses substring of a given string.
Expected Output:
Original Parentheses string: (()))
Length of longest parentheses: 4
17. Sum of Multiples of 3 or 7 Below 100 Variants
The natural numbers below 10 that are multiples of 3 or 7 are 3, 7, 6 and 9. The sum of these multiples is 25.
Write a C program to find the sum of all the multiples of 3 or 7 below 100.
Expected Output:
2208
18. Sum of Even-Valued Fibonacci Terms Variants
In mathematics, the Fibonacci numbers, commonly denoted Fn form a sequence, called the Fibonacci sequence, such that each number is the sum of the two preceding ones, starting from 0 and 1. That is, and for n > 1. By starting with 1 and 2, the first 10 terms will be: 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, . . .
Write a C program to find the sum of the even-valued terms from the terms in the Fibonacci sequence whose values do not exceed one million.
Expected Output:
10
19. Largest Prime Factor Variants
Write a C program to find the largest prime factor of the number 438927456.
Expected Output:
415651
20. Largest Palindrome Product Variants
A palindrome is a word, number, phrase, or other sequence of characters which reads the same backward as forward, such as taco cat or madam or racecar or the number 10801. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.
Write a C program to find the largest palindrome made from the product of two 3-digit numbers.
Expected Output:
906609
21. Smallest Multiple for 1 to 20 Variants
2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder.
Write a C program to find the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?
Expected Output:
232792560
22. Difference Between Sum of Squares and Square of Sum Variants
The sum of the squares of the first ten natural numbers is,
12 + 22 + ... + 102 = 385
The square of the sum of the first ten natural numbers is,
(1 + 2 + ... + 10)2 = 552 = 3025
Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025 − 385 = 2640.
Write a C program to find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum.
Expected Output:
25164150
23. 1001st Prime Number Variants
By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.
The first six prime numbers are 2, 3, 5, 7, 11, and 13.
Write a C program to get the 1001st prime number?
Expected Output:
7927
24. Greatest Product in 20x20 Grid Variants
The four adjacent digits in the 1000-digit number that have the greatest product are 9 × 9 × 8 × 9 = 5832.
73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450.
Write a C program to find the thirteen adjacent digits in the 1000-digit number that have the greatest product. What is the value of this product?
Expected Output:
40824
25. First Missing Positive Integer Variants
A Pythagorean triplet is a set of three natural numbers, x < y < z, for which,
x2 + y2 = z2
For example, 32 + 42 = 9 + 16 = 25 = 52.
There exists exactly one Pythagorean triplet for which x +y + z = 1000.
Write a C program to find the product of xyz.
Expected Output:
Numbers are: 200, 375, 425 Product of x, y, z is : 31875000
26. Minimum Insertions for Palindrome Variants
A prime number is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways of writing it as a product, 1 × 5 or 5 × 1, involve 5 itself. However, 6 is composite because it is the product of two numbers (2 × 3) that are both smaller than 6.
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
Write a C program to find the sum of all prime numbers below ten thousand.
Expected Output:
5736396
27. Ascending Prime Numbers (Strictly Increasing Digits) Variants
In the 20×20 grid below, four numbers along a diagonal line have been marked in red.
08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08
49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00
81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65
52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91
22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80
24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50
32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70
67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21
24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72
21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95
78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92
16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57
86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58
19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40
04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66
88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69
04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36
20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16
20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54
01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48
The product of these numbers is 26 × 63 × 78 × 14 = 1788696.
Write a C program to find the greatest product of four adjacent numbers in the same direction (up, down, left, right, or diagonally) in the 20×20 grid.
Expected Output:
70600674
28. Descending Prime Numbers (Strictly Decreasing Digits) Variants
Write a C program to find the first missing positive integer in a given unsorted integer array.
Expected Output:
2
29. Attractive Numbers Up to 100 Variants
Write a C program to find the minimum number of characters that must be inserted into a given string with no whitespace characters to make it a palindrome.
Sample Input: pps
Output: 1
30. Colorful Number Test Variants
Write a C program to create and display all prime numbers in strictly ascending decimal digit order.
Sample Data: 2, 3, 5, 7, 13, 17, 19, 23, 29, 37, 47, 59, 67, 79,..
31. Progression Type & Next Member Variants
Write a C program to find the type of progression (arithmetic progression/geometric progression) and the next successive member of the three successive members of a sequence.
Sample Data: 2, 6, 18, 54, ..
32. Descending Prime Numbers (C# Sharp to C Adaptation) Variants
Write a C# Sharp program to create and display all prime numbers in strictly descending decimal digit order.
Sample Data:
2, 3, 5, 7, 31, 41, 43, 53, 61, 71, 73, 83, 97, 421, 431.....
33. Attractive Numbers Generation Variants
Write a C program to generate attractive numbers up to 100.
34. Colorful Number Test Subroutine Variants
Write a C program (subroutine, function, procedure, whatever it may be called in your language) to test if a number is a colorful number or not.
Sample Data:
Colorful numbers less than 100:
0 1 2 3 4 5 6 7 8 9
23 24 25 26 27 28 29 32 34 35
36 37 38 39 42 43 45 46 47 48
49 52 53 54 56 57 58 59 62 63
64 65 67 68 69 72 73 74 75 76
78 79 82 83 84 85 86 87 89 92
93 94 95 96 97 98
35. Text Calendar Generation Variants
Write a C program to generate a text calendar for any given year.
Sample Data:
C Programming Code Editor:
More to Come !
Do not submit any solution of the above exercises at here, if you want to contribute go to the appropriate exercise page.