mirror of
https://github.com/TheAlgorithms/C
synced 2024-11-21 21:11:57 +03:00
93 lines
2.7 KiB
C
93 lines
2.7 KiB
C
/**
|
|
* @file
|
|
* @author [serturx](https://github.com/serturx/)
|
|
* @brief Encode a null terminated string using [Run-length encoding](https://en.wikipedia.org/wiki/Run-length_encoding)
|
|
* @details
|
|
* Run-length encoding is a lossless compression algorithm.
|
|
* It works by counting the consecutive occurences symbols
|
|
* and encodes that series of consecutive symbols into the
|
|
* counted symbol and a number denoting the number of
|
|
* consecutive occorences.
|
|
*
|
|
* For example the string "AAAABBCCD" gets encoded into "4A2B2C1D"
|
|
*
|
|
*/
|
|
|
|
#include <stdio.h> /// for IO operations
|
|
#include <string.h> /// for string functions
|
|
#include <stdlib.h> /// for malloc/free
|
|
#include <assert.h> /// for assert
|
|
|
|
/**
|
|
* @brief Encodes a null-terminated string using run-length encoding
|
|
* @param str String to encode
|
|
* @return char* Encoded string
|
|
*/
|
|
|
|
char* run_length_encode(char* str) {
|
|
int str_length = strlen(str);
|
|
int encoded_index = 0;
|
|
|
|
//allocate space for worst-case scenario
|
|
char* encoded = malloc(2 * strlen(str));
|
|
|
|
//temp space for int to str conversion
|
|
char int_str[20];
|
|
|
|
for(int i = 0; i < str_length; ++i) {
|
|
int count = 0;
|
|
char current = str[i];
|
|
|
|
//count occurences
|
|
while(current == str[i + count]) count++;
|
|
|
|
i += count - 1;
|
|
|
|
//convert occurrence amount to string and write to encoded string
|
|
sprintf(int_str, "%d", count);
|
|
int int_str_length = strlen(int_str);
|
|
strncpy(&encoded[encoded_index], int_str, strlen(int_str));
|
|
|
|
//write current char to encoded string
|
|
encoded_index += strlen(int_str);
|
|
encoded[encoded_index] = current;
|
|
++encoded_index;
|
|
}
|
|
|
|
//null terminate string and move encoded string to compacted memory space
|
|
encoded[encoded_index] = '\0';
|
|
char* compacted_string = malloc(strlen(encoded) + 1);
|
|
strcpy(compacted_string, encoded);
|
|
|
|
free(encoded);
|
|
|
|
return compacted_string;
|
|
}
|
|
|
|
/**
|
|
* @brief Self-test implementations
|
|
* @returns void
|
|
*/
|
|
static void test() {
|
|
char* test;
|
|
test = run_length_encode("aaaaaaabbbaaccccdefaadr");
|
|
assert(!strcmp(test, "7a3b2a4c1d1e1f2a1d1r"));
|
|
free(test);
|
|
test = run_length_encode("lidjhvipdurevbeirbgipeahapoeuhwaipefupwieofb");
|
|
assert(!strcmp(test, "1l1i1d1j1h1v1i1p1d1u1r1e1v1b1e1i1r1b1g1i1p1e1a1h1a1p1o1e1u1h1w1a1i1p1e1f1u1p1w1i1e1o1f1bq"));
|
|
free(test);
|
|
test = run_length_encode("htuuuurwuquququuuaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaahghghrw");
|
|
assert(!strcmp(test, "1h1t4u1r1w1u1q1u1q1u1q3u76a1h1g1h1g1h1r1w"));
|
|
free(test);
|
|
}
|
|
|
|
/**
|
|
* @brief Main function
|
|
* @returns 0 on exit
|
|
*/
|
|
int main() {
|
|
test(); // run self-test implementations
|
|
printf("All tests have passed!\n");
|
|
return 0;
|
|
}
|