feat(solutions): add prefix-suffix/c/function

challenges/prefix-suffix/solutions/c/function/README.md

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+# prefix-suffix/c/function
+
+Created by [@Divlo](https://github.com/Divlo) on 2 December 2021.

challenges/prefix-suffix/solutions/c/function/character.c

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+#include "character.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+void character_append(char* string, char character) {
+  size_t length = strlen(string);
+  string[length] = character;
+  string[length + 1] = '\0';
+}

challenges/prefix-suffix/solutions/c/function/character.h

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+#ifndef __CHARACTER__
+#define __CHARACTER__
+
+/**
+ * @brief Append a character to a string, assuming string points to an array
+ * with enough space.
+ *
+ * @param string
+ * @param character
+ */
+void character_append(char* string, char character);
+
+#endif

challenges/prefix-suffix/solutions/c/function/input.c

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+#include "input.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "character.h"
+
+char* input() {
+  char character;
+  size_t length = 1;
+  char* string = malloc(length * sizeof(char));
+  *string = '\0';
+  while ((character = getchar()) != '\n' && character != EOF) {
+    length++;
+    string = realloc(string, length * sizeof(char));
+    character_append(string, character);
+  }
+  return string;
+}

challenges/prefix-suffix/solutions/c/function/input.h

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+#ifndef __INPUT__
+#define __INPUT__
+
+/**
+ * @brief Read a line from stdin.
+ *
+ * @return char*
+ */
+char* input();
+
+#endif

challenges/prefix-suffix/solutions/c/function/solution.c

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+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "input.h"
+#include "string.h"
+
+int main() {
+  char* string = input();
+  char* string2 = input();
+  bool is_preffix = string_starts_with(string, string2);
+  bool is_suffix = string_ends_with(string, string2);
+  free(string);
+  free(string2);
+  printf("%s\n", is_preffix ? "true" : "false");
+  printf("%s\n", is_suffix ? "true" : "false");
+  return EXIT_SUCCESS;
+}

challenges/prefix-suffix/solutions/c/function/string.c

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+#include "string.h"
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "character.h"
+
+bool string_starts_with(char* string, char* prefix) {
+  size_t string_length = strlen(string);
+  size_t prefix_length = strlen(prefix);
+  bool is_prefix = string_length >= prefix_length;
+  for (size_t index = 0; index < prefix_length && index < string_length && is_prefix; index++) {
+    if (prefix[index] != string[index]) {
+      is_prefix = false;
+    }
+  }
+  return is_prefix;
+}
+
+bool string_ends_with(char* string, char* suffix) {
+  size_t string_length = strlen(string);
+  size_t suffix_length = strlen(suffix);
+  int index_start_of_the_end = string_length - suffix_length;
+  bool is_suffix = true;
+  if (index_start_of_the_end < 0) {
+    is_suffix = false;
+  } else {
+    size_t suffix_index = 0;
+    for (size_t string_index = index_start_of_the_end; string_index < string_length && is_suffix; string_index++) {
+      if (string[string_index] != suffix[suffix_index]) {
+        is_suffix = false;
+      }
+      suffix_index++;
+    }
+  }
+  return is_suffix;
+}

challenges/prefix-suffix/solutions/c/function/string.h

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+#ifndef __STRING__
+#define __STRING__
+
+#include <stdbool.h>
+
+/**
+ * @brief Returns true if the string is a prefix of another string.
+ *
+ * @param string
+ * @param prefix
+ * @return true
+ * @return false
+ */
+bool string_starts_with(char* string, char* prefix);
+
+/**
+ * @brief Returns true if the string is a suffix of another string.
+ *
+ * @param string
+ * @param suffix
+ * @return true
+ * @return false
+ */
+bool string_ends_with(char* string, char* suffix);
+
+#endif