fix(solutions): fix: more memory issues thanks to -fsanitize=address flag with gcc

challenges/rotate-2-dimensional-array-90-degrees/solutions/c/function/string.h

@@ -0,0 +1,35 @@
+#ifndef __STRING__
+#define __STRING__
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/**
+ * @brief Return the length of a string (excluding '\0').
+ *
+ * @param string
+ * @return size_t
+ */
+size_t string_get_length(const char* string);
+
+/**
+ * @brief Return the copy of a string.
+ *
+ * @param string
+ * @return string_t
+ */
+char* string_copy(const char* string);
+
+/**
+ * @brief Split a string into substrings using the specified separator and return them as an array and update the pointer `result_size` to the resulting size of the created array.
+ *
+ * @param string
+ * @param separator
+ * @param result_size
+ * @return string_t*
+ */
+char** string_split(const char* string, char separator, size_t* result_size);
+
+#endif