How to compress a string and replace duplicates with its count using C?

How to compress a string and replace duplicates with its count using C?

Compressing a string and replacing consecutive duplicates with their count can be achieved in C by iterating through the string, counting consecutive occurrences of each character, and constructing a new compressed string based on these counts. Here's a step-by-step approach to implement this:

Steps to Implement String Compression in C

  1. Initialize Variables:

    • Use a loop to iterate through the string character by character.
    • Count consecutive occurrences of each character.

  2. Construct Compressed String:

    • Append each unique character to a new string along with its count of consecutive occurrences.

  3. Output the Compressed String:

    • Print or store the compressed string as required.

Example Implementation:

Here's a simple example in C that compresses a string and replaces consecutive duplicates with their count:

#include <stdio.h> #include <string.h> void compressString(const char* str) { int len = strlen(str); if (len == 0) { printf("Compressed string: \n"); return; } char compressed[len * 2]; // Maximum possible length of compressed string int index = 0; for (int i = 0; i < len; i++) { int count = 1; while (i < len - 1 && str[i] == str[i + 1]) { count++; i++; } index += sprintf(&compressed[index], "%c%d", str[i], count); } compressed[index] = '\0'; // Null-terminate the string printf("Compressed string: %s\n", compressed); } int main() { const char* input = "aabbbcccccddeee"; printf("Original string: %s\n", input); compressString(input); return 0; }

Explanation:

  • compressString Function:

    • len calculates the length of the input string str.
    • compressed array is used to construct the compressed string.
    • index keeps track of the current position in the compressed array.
    • The for loop iterates through each character in str.
    • count keeps track of consecutive occurrences of the current character.
    • The sprintf function appends the character and its count to the compressed string.

  • main Function:

    • Demonstrates how to use compressString with an example input string "aabbbcccccddeee".
    • Prints the original string and the compressed string.

Output:

Original string: aabbbcccccddeee Compressed string: a2b3c5d2e3

Notes:

  • This example assumes that the input string contains only lowercase alphabetical characters. Modify the logic as needed for other character sets or requirements.
  • Ensure that the compressed array is large enough to hold the compressed string. In this example, it's sized as len * 2 to account for the worst-case scenario.
  • Error handling for edge cases (such as empty strings) can be added based on specific requirements.

This implementation efficiently compresses the string by replacing consecutive duplicates with their counts, demonstrating a basic approach to string compression in C. Adjustments can be made for different requirements or optimizations, depending on your specific use case.

Examples

  1. How to count duplicate characters in a string in C?

    • Description: This query seeks methods to count occurrences of duplicate characters in a given string using C.
    • Code:
      #include <stdio.h> #include <string.h> void countDuplicates(const char *str) { int count[256] = {0}; // Assuming ASCII characters for (int i = 0; str[i]; i++) { count[str[i]]++; } for (int i = 0; i < 256; i++) { if (count[i] > 1) { printf("%c appears %d times\n", i, count[i]); } } } int main() { const char *input = "Hello World"; countDuplicates(input); return 0; }

  2. How to compress a string by replacing consecutive duplicates with a single character in C?

    • Description: This query aims to compress a string by replacing consecutive duplicate characters with a single character using C.
    • Code:
      #include <stdio.h> #include <string.h> void compressString(char *str) { int n = strlen(str); if (n <= 1) { return; } int j = 0; for (int i = 0; i < n; i++) { str[j++] = str[i]; while (i < n - 1 && str[i] == str[i + 1]) { i++; } } str[j] = '\0'; } int main() { char str[] = "aaabbbcccdddeee"; compressString(str); printf("Compressed string: %s\n", str); return 0; }

  3. How to replace duplicate characters with their count in a string in C?

    • Description: This query looks for methods to replace duplicate characters in a string with their respective counts using C.
    • Code:
      #include <stdio.h> #include <string.h> void replaceDuplicatesWithCount(char *str) { int n = strlen(str); if (n <= 1) { return; } int count = 1; for (int i = 1, j = 0; i <= n; i++) { if (str[i] == str[i - 1]) { count++; } else { str[j++] = str[i - 1]; if (count > 1) { char countStr[10]; sprintf(countStr, "%d", count); strcat(str, countStr); j += strlen(countStr); count = 1; } } } } int main() { char str[] = "aaabbbcccdddeee"; replaceDuplicatesWithCount(str); printf("Modified string: %s\n", str); return 0; }

  4. How to remove duplicate characters from a string in C?

    • Description: This query focuses on techniques to remove duplicate characters entirely from a given string using C.
    • Code:
      #include <stdio.h> #include <string.h> void removeDuplicates(char *str) { int len = strlen(str); if (len < 2) { return; } int tail = 1; for (int i = 1; i < len; ++i) { int j; for (j = 0; j < tail; ++j) { if (str[i] == str[j]) break; } if (j == tail) { str[tail++] = str[i]; } } str[tail] = '\0'; } int main() { char str[] = "aaabbbcccdddeee"; removeDuplicates(str); printf("String after removing duplicates: %s\n", str); return 0; }

  5. How to find the most frequent character in a string in C?

    • Description: This query aims to find the character that appears most frequently in a given string using C.
    • Code:
      #include <stdio.h> #include <string.h> void findMostFrequent(char *str) { int count[256] = {0}; int maxCount = 0; char result; for (int i = 0; str[i] != '\0'; i++) { count[str[i]]++; if (count[str[i]] > maxCount) { maxCount = count[str[i]]; result = str[i]; } } printf("Most frequent character: %c\n", result); } int main() { char str[] = "hello world"; findMostFrequent(str); return 0; }

  6. How to count occurrences of each character in a string in C?

    • Description: This query seeks methods to count occurrences of each character in a given string using C.
    • Code:
      #include <stdio.h> #include <string.h> void countCharacterOccurrences(char *str) { int count[256] = {0}; // Assuming ASCII characters for (int i = 0; str[i] != '\0'; i++) { count[str[i]]++; } for (int i = 0; i < 256; i++) { if (count[i] != 0) { printf("%c occurs %d times\n", i, count[i]); } } } int main() { char str[] = "hello world"; countCharacterOccurrences(str); return 0; }

  7. How to sort characters in a string alphabetically in C?

    • Description: This query focuses on sorting characters within a string alphabetically using C.
    • Code:
      #include <stdio.h> #include <string.h> void sortString(char *str) { int n = strlen(str); for (int i = 0; i < n - 1; i++) { for (int j = i + 1; j < n; j++) { if (str[i] > str[j]) { char temp = str[i]; str[i] = str[j]; str[j] = temp; } } } } int main() { char str[] = "hello world"; sortString(str); printf("Sorted string: %s\n", str); return 0; }

  8. How to reverse a string in C?

    • Description: This query seeks methods to reverse the characters within a string using C.
    • Code:
      #include <stdio.h> #include <string.h> void reverseString(char *str) { int len = strlen(str); for (int i = 0; i < len / 2; i++) { char temp = str[i]; str[i] = str[len - i - 1]; str[len - i - 1] = temp; } } int main() { char str[] = "hello world"; reverseString(str); printf("Reversed string: %s\n", str); return 0; }

  9. How to concatenate strings in C?

    • Description: This query looks for methods to concatenate multiple strings into one using C.
    • Code:
      #include <stdio.h> #include <string.h> void concatenateStrings(char *str1, char *str2) { strcat(str1, str2); } int main() { char str1[50] = "Hello "; char str2[] = "World"; concatenateStrings(str1, str2); printf("Concatenated string: %s\n", str1); return 0; }

  10. How to convert a string to lowercase in C?

    • Description: This query aims to convert all characters of a string to lowercase using C.
    • Code:
      #include <stdio.h> #include <string.h> #include <ctype.h> void stringToLower(char *str) { int len = strlen(str); for (int i = 0; i < len; i++) { str[i] = tolower(str[i]); } } int main() { char str[] = "Hello World"; stringToLower(str); printf("Lowercase string: %s\n", str); return 0; }

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