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

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

@@ -0,0 +1,32 @@
+#include "string.h"
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "character.h"
+
+size_t string_total_occurrences_of_character(char* string, char character) {
+  size_t result = 0;
+  size_t string_length = strlen(string);
+  for (size_t index = 0; index < string_length; index++) {
+    char current_character = string[index];
+    if (current_character == character) {
+      result += 1;
+    }
+  }
+  return result;
+}
+
+char string_first_non_repeating_character(char* string) {
+  size_t string_length = strlen(string);
+  char result = ""[0];
+  for (size_t index = 0; index < string_length; index++) {
+    char character = string[index];
+    if (string_total_occurrences_of_character(string, character) == 1) {
+      result = character;
+      break;
+    }
+  }
+  return result;
+}