String in C Exercises & Solutions

String Manipulation in C: Exercises and Solutions

Strings are the fabric of information in C programming. Mastering their manipulation techniques is crucial for building strong programs. This guide dives into a selection of string exercises and their solutions, equipping you with the practical skills to navigate the world of string operations.

1. Basic String Processing

Exercise 1: Print String Length

Write a program to input a string and print its length.

Solution:

C

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

int main() {
  char str[100];
  int length;

  printf("Enter a string: ");
  fgets(str, 100, stdin); // read string from user

  // calculate length using strlen
  length = strlen(str);

  // remove newline character from length
  length--;

  printf("The string length is: %d\n", length);

  return 0;
}

Explanation:

• We include stdio.h and string.h for input/output and string functions.
• We declare a character array str to store the user-entered string and an integer length for its length.
• fgets reads the string from user input, including the newline character.
• strlen calculates the string length (excluding the null terminator).
• We subtract 1 from length to account for the newline character.
• Finally, we print the actual string length.

Exercise 2: Count Uppercase and Lowercase Characters

Write a program to count the number of uppercase and lowercase characters in a string.

Solution:

C

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

int main() {
  char str[100];
  int uppercaseCount = 0, lowercaseCount = 0;

  printf("Enter a string: ");
  fgets(str, 100, stdin);

  for (int i = 0; str[i] != '\0'; i++) {
    if (isupper(str[i])) {
      uppercaseCount++;
    } else if (islower(str[i])) {
      lowercaseCount++;
    }
  }

  printf("Uppercase characters: %d\n", uppercaseCount);
  printf("Lowercase characters: %d\n", lowercaseCount);

  return 0;
}

Explanation:

• We include stdio.h and ctype.h for input/output and character classification functions.
• We declare variables to store counts for uppercase and lowercase characters.
• We iterate through the string using a loop until the null terminator is reached.
• isupper and islower check if a character is uppercase or lowercase, respectively.
• We increment the corresponding count based on the character type.
• Finally, we print the counts for both uppercase and lowercase characters.

2. String Manipulation Advanced

Exercise 3: Concatenate Two Strings

Write a program to concatenate two strings and store the result in a new string.

Solution:

C

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

int main() {
  char str1[50], str2[50], str3[100];

  printf("Enter first string: ");
  fgets(str1, 50, stdin);

  printf("Enter second string: ");
  fgets(str2, 50, stdin);

  // remove newline characters
  str1[strlen(str1) - 1] = '\0';
  str2[strlen(str2) - 1] = '\0';

  // concatenate strings using strcat
  strcat(str3, str1);
  strcat(str3, str2);

  printf("Combined string: %s\n", str3);

  return 0;
}

Explanation:

• We declare three character arrays to store the two input strings and the combined string.
• We read the two strings from the user using fgets.
• We remove the newline characters from the input strings before concatenation.
• strcat appends the contents of str2 to the end of str3 (which already contains str1).
• Finally, we print the combined string.

Exercise 4: Reverse a String

Write a program to reverse a string in-place.

Solution:

C

  int n = strlen(str);
  for (int i = 0; i < n / 2; i++) {
    char temp = str[i];
    str[i] = str[n - 1 - i];
    str[n - 1 - i] = temp;
  }
}

int main() {
  char str[100];

  printf("Enter a string: ");
  fgets(str, 100, stdin);

  // remove newline character
  str[strlen(str) - 1] = '\0';

  reverseString(str);

  printf("Reversed string: %s\n", str);

  return 0;
}

Explanation:

• We define a function reverseString that takes a character array as input.
• We use a loop that iterates half the length of the string.
• Inside the loop, we swap the characters at opposite ends using a temporary variable to hold the value during the exchange.
• This effectively reverses the order of characters within the original string.
• The main function reads the string from the user, removes the newline character, calls the reverseString function, and then prints the reversed string.

Bonus Exercise:

• Implement a function to compare two strings for case-insensitive comparison.

Remember, these are just a few examples. Explore further string manipulation exercises like finding sub-strings, replacing characters, and counting occurrences of specific letters to refine your string handling skills and unlock the full potential of string operations in C programming.

Feel free to ask if you have any questions or need me to elaborate on any specific aspects of string manipulation in C.