feat(solutions): add consecutive-numbers/c/function

challenges/consecutive-numbers/solutions/c/function/README.md

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+# consecutive-numbers/c/function
+
+Created by [@Divlo](https://github.com/Divlo) on 12 October 2021.

challenges/consecutive-numbers/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/consecutive-numbers/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/consecutive-numbers/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/consecutive-numbers/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/consecutive-numbers/solutions/c/function/solution.c

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+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "input.h"
+
+void print_couple(int* numbers, size_t couple_length) {
+  for (size_t index = 0; index < couple_length; index++) {
+    printf("%d", numbers[index]);
+    if (index != couple_length - 1) {
+      printf(" ; ");
+    }
+  }
+  printf("\n");
+}
+
+int main() {
+  size_t couple_length;
+  scanf("%ld\n", &couple_length);
+  char* string = input();
+  char* token = strtok(string, " ; ");
+  size_t numbers_length = 1;
+  int* numbers = malloc(sizeof(int) * numbers_length);
+  while (token != NULL) {
+    if (strcmp(token, ";") != 0) {
+      int number;
+      sscanf(token, "%d", &number);
+      numbers[numbers_length - 1] = number;
+      numbers_length++;
+      numbers = realloc(numbers, sizeof(int) * numbers_length);
+    }
+    token = strtok(NULL, " ");
+  }
+
+  for (size_t index = 0; index < numbers_length; index++) {
+    int* consecutive = malloc(sizeof(int) * couple_length);
+    consecutive[0] = numbers[index];
+    size_t consecutive_length = 1;
+    for (size_t couple_index = 1; couple_index < couple_length; couple_index++) {
+      bool is_last_number = index + couple_index == numbers_length;
+      if (is_last_number) {
+        break;
+      }
+      if (numbers[index] + couple_index == numbers[index + couple_index]) {
+        consecutive[consecutive_length] = numbers[index] + couple_index;
+        consecutive_length++;
+      }
+      bool is_consecutive = consecutive_length == couple_length;
+      if (is_consecutive) {
+        print_couple(consecutive, consecutive_length);
+      }
+    }
+    free(consecutive);
+  }
+  free(numbers);
+  return EXIT_SUCCESS;
+}