From 9621751a4d843c1dc274ffead54f55e212dba2ba Mon Sep 17 00:00:00 2001
From: Divlo <contact@divlo.fr>
Date: Mon, 8 Nov 2021 16:56:46 +0100
Subject: [PATCH] feat(solutions): add `heap-algorithm/c/function`

---
 .../solutions/c/function/README.md            |  3 ++
 .../solutions/c/function/character.c          | 10 +++++
 .../solutions/c/function/character.h          | 13 ++++++
 .../solutions/c/function/input.c              | 19 ++++++++
 .../solutions/c/function/input.h              | 11 +++++
 .../solutions/c/function/solution.c           | 45 +++++++++++++++++++
 6 files changed, 101 insertions(+)
 create mode 100644 challenges/heap-algorithm/solutions/c/function/README.md
 create mode 100644 challenges/heap-algorithm/solutions/c/function/character.c
 create mode 100644 challenges/heap-algorithm/solutions/c/function/character.h
 create mode 100644 challenges/heap-algorithm/solutions/c/function/input.c
 create mode 100644 challenges/heap-algorithm/solutions/c/function/input.h
 create mode 100644 challenges/heap-algorithm/solutions/c/function/solution.c

diff --git a/challenges/heap-algorithm/solutions/c/function/README.md b/challenges/heap-algorithm/solutions/c/function/README.md
new file mode 100644
index 0000000..1a28ad6
--- /dev/null
+++ b/challenges/heap-algorithm/solutions/c/function/README.md
@@ -0,0 +1,3 @@
+# heap-algorithm/c/function
+
+Created by [@Divlo](https://github.com/Divlo) on 8 November 2021.
diff --git a/challenges/heap-algorithm/solutions/c/function/character.c b/challenges/heap-algorithm/solutions/c/function/character.c
new file mode 100644
index 0000000..49d4f00
--- /dev/null
+++ b/challenges/heap-algorithm/solutions/c/function/character.c
@@ -0,0 +1,10 @@
+#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';
+}
diff --git a/challenges/heap-algorithm/solutions/c/function/character.h b/challenges/heap-algorithm/solutions/c/function/character.h
new file mode 100644
index 0000000..0fab88f
--- /dev/null
+++ b/challenges/heap-algorithm/solutions/c/function/character.h
@@ -0,0 +1,13 @@
+#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
diff --git a/challenges/heap-algorithm/solutions/c/function/input.c b/challenges/heap-algorithm/solutions/c/function/input.c
new file mode 100644
index 0000000..c07bb6d
--- /dev/null
+++ b/challenges/heap-algorithm/solutions/c/function/input.c
@@ -0,0 +1,19 @@
+#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;
+}
diff --git a/challenges/heap-algorithm/solutions/c/function/input.h b/challenges/heap-algorithm/solutions/c/function/input.h
new file mode 100644
index 0000000..d432398
--- /dev/null
+++ b/challenges/heap-algorithm/solutions/c/function/input.h
@@ -0,0 +1,11 @@
+#ifndef __INPUT__
+#define __INPUT__
+
+/**
+ * @brief Read a line from stdin.
+ *
+ * @return char*
+ */
+char* input();
+
+#endif
diff --git a/challenges/heap-algorithm/solutions/c/function/solution.c b/challenges/heap-algorithm/solutions/c/function/solution.c
new file mode 100644
index 0000000..8d5bafb
--- /dev/null
+++ b/challenges/heap-algorithm/solutions/c/function/solution.c
@@ -0,0 +1,45 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "input.h"
+
+char *swap(char *string, size_t index_from, size_t index_target) {
+  size_t string_length = strlen(string);
+  char *result = malloc(sizeof(char *) * (string_length));
+  for (size_t index = 0; index < string_length; index++) {
+    if (index == index_from) {
+      result[index] = string[index_target];
+    } else if (index == index_target) {
+      result[index] = string[index_from];
+    } else {
+      result[index] = string[index];
+    }
+  }
+  return result;
+}
+
+void heap_algorithm(unsigned long number_of_elements_to_operate, char *string) {
+  if (number_of_elements_to_operate == 1) {
+    printf("%s\n", string);
+  } else {
+    heap_algorithm(number_of_elements_to_operate - 1, string);
+    for (size_t index = 0; index < number_of_elements_to_operate - 1; index++) {
+      bool is_even = number_of_elements_to_operate % 2 == 0;
+      if (!is_even) {
+        string = swap(string, index, number_of_elements_to_operate - 1);
+      } else {
+        string = swap(string, 0, number_of_elements_to_operate - 1);
+      }
+      heap_algorithm(number_of_elements_to_operate - 1, string);
+    }
+  }
+}
+
+int main() {
+  char *string = input();
+  size_t string_length = strlen(string);
+  heap_algorithm(string_length, string);
+  return EXIT_SUCCESS;
+}