Add run length encoding

misc/run_length_encoding.c

@@ -0,0 +1,75 @@
+/**
+ * @file run_length_encoding.c
+ * @author [serturx](https://github.com/serturx/)
+ * @brief Encode a null terminated string using [Run-length encoding](https://en.wikipedia.org/wiki/Run-length_encoding)
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <assert.h>
+
+/**
+ * @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;
+}
+
+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);
+}
+
+int main() {
+    test();
+    printf("Tests passed.");
+    return 0;
+}