mirror of
https://github.com/TheAlgorithms/C
synced 2024-11-29 00:33:14 +03:00
93 lines
2.7 KiB
C
93 lines
2.7 KiB
C
/**
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* @file
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* @author [serturx](https://github.com/serturx/)
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* @brief Encode a null terminated string using [Run-length encoding](https://en.wikipedia.org/wiki/Run-length_encoding)
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* @details
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* Run-length encoding is a lossless compression algorithm.
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* It works by counting the consecutive occurences symbols
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* and encodes that series of consecutive symbols into the
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* counted symbol and a number denoting the number of
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* consecutive occorences.
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*
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* For example the string "AAAABBCCD" gets encoded into "4A2B2C1D"
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*
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*/
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#include <stdio.h> /// for IO operations
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#include <string.h> /// for string functions
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#include <stdlib.h> /// for malloc/free
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#include <assert.h> /// for assert
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/**
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* @brief Encodes a null-terminated string using run-length encoding
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* @param str String to encode
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* @return char* Encoded string
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*/
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char* run_length_encode(char* str) {
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int str_length = strlen(str);
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int encoded_index = 0;
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//allocate space for worst-case scenario
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char* encoded = malloc(2 * strlen(str));
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//temp space for int to str conversion
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char int_str[20];
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for(int i = 0; i < str_length; ++i) {
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int count = 0;
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char current = str[i];
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//count occurences
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while(current == str[i + count]) count++;
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i += count - 1;
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//convert occurrence amount to string and write to encoded string
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sprintf(int_str, "%d", count);
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int int_str_length = strlen(int_str);
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strncpy(&encoded[encoded_index], int_str, strlen(int_str));
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//write current char to encoded string
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encoded_index += strlen(int_str);
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encoded[encoded_index] = current;
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++encoded_index;
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}
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//null terminate string and move encoded string to compacted memory space
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encoded[encoded_index] = '\0';
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char* compacted_string = malloc(strlen(encoded) + 1);
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strcpy(compacted_string, encoded);
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free(encoded);
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return compacted_string;
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}
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/**
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* @brief Self-test implementations
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* @returns void
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*/
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static void test() {
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char* test;
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test = run_length_encode("aaaaaaabbbaaccccdefaadr");
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assert(!strcmp(test, "7a3b2a4c1d1e1f2a1d1r"));
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free(test);
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test = run_length_encode("lidjhvipdurevbeirbgipeahapoeuhwaipefupwieofb");
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assert(!strcmp(test, "1l1i1d1j1h1v1i1p1d1u1r1e1v1b1e1i1r1b1g1i1p1e1a1h1a1p1o1e1u1h1w1a1i1p1e1f1u1p1w1i1e1o1f1bq"));
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free(test);
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test = run_length_encode("htuuuurwuquququuuaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaahghghrw");
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assert(!strcmp(test, "1h1t4u1r1w1u1q1u1q1u1q3u76a1h1g1h1g1h1r1w"));
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free(test);
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}
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/**
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* @brief Main function
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* @returns 0 on exit
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*/
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int main() {
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test(); // run self-test implementations
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printf("All tests have passed!\n");
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return 0;
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}
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