feat(solutions): add first-non-repeating-character/c/function

challenges/first-non-repeating-character/solutions/c/function/string.h

@@ -0,0 +1,23 @@
+#ifndef STRING_H
+#define STRING_H
+
+#include <stdlib.h>
+
+/**
+ * @brief Returns the total number of occurrences of the given character in the string.
+ *
+ * @param string
+ * @param character
+ * @return size_t
+ */
+size_t string_total_occurrences_of_character(char* string, char character);
+
+/**
+ * @brief Returns the first non-repeating character in the given string.
+ *
+ * @param string
+ * @return char*
+ */
+char string_first_non_repeating_character(char* string);
+
+#endif