From 4056cf92937fa6a0460d16b5cb8d5398cd2503b8 Mon Sep 17 00:00:00 2001
From: mossfet <root@mossfet.xyz>
Date: Fri, 31 Mar 2023 12:27:08 +0100
Subject: [PATCH] First commit

---
 .gitignore       |  1 +
 main.c           | 17 +++++++++
 priority_queue.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++
 priority_queue.h | 27 +++++++++++++++
 4 files changed, 134 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 main.c
 create mode 100644 priority_queue.c
 create mode 100644 priority_queue.h

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..cba7efc
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+a.out
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..1eafaf7
--- /dev/null
+++ b/main.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "priority_queue.h"
+int main (int argc, char** argv) {
+	PriorityQueue priority_queue = { (int*)calloc(10, sizeof(int)), 0, 5};
+	int i = 0;
+	while (true) {
+		insert(&priority_queue, i);
+		if (i % 100000 == 0) {
+			printf("%i\n", i);
+		}
+		i++;
+	}
+	return 0;
+}
+
+
diff --git a/priority_queue.c b/priority_queue.c
new file mode 100644
index 0000000..fd8c131
--- /dev/null
+++ b/priority_queue.c
@@ -0,0 +1,89 @@
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+
+#include "priority_queue.h"
+
+void insert(PriorityQueue *priority_queue, int item) {
+	if (priority_queue->max_item == priority_queue->size - 1) {
+		printf("Reallocating from %i to %i!\n", priority_queue->size, priority_queue->size*2);
+		priority_queue->array = realloc(priority_queue->array, priority_queue->size*2*sizeof(int));
+		if (priority_queue->array == NULL) {
+			printf("That's a null pointer!\n");
+		}
+		priority_queue->size *= 2;
+	}
+	priority_queue->array[priority_queue->max_item] = item;
+	bubble_up(priority_queue, priority_queue->max_item);
+	priority_queue->max_item++;
+}
+
+int extract (PriorityQueue *priority_queue) {
+	int item = priority_queue->array[0];
+	priority_queue->array[0] = priority_queue->array[priority_queue->max_item - 1];
+	bubble_down(priority_queue, 0);
+	return item;
+}
+
+size_t parent (size_t index) {
+	return (index-1)/2;
+}
+
+size_t l_child (size_t index) {
+	return (2*index)+1;
+}
+
+size_t r_child (size_t index) {
+	return (2*index)+2;
+}
+
+void bubble_up (PriorityQueue *priority_queue, size_t index) {
+	if (index == 0) {
+		return;
+	}
+	if (compare(priority_queue, index, parent(index))) {
+		swap_parent(priority_queue, index);
+		bubble_up (priority_queue, parent(index));
+	}
+}
+
+void bubble_down (PriorityQueue *priority_queue, size_t index) {
+	size_t min = index;
+	size_t left = l_child (index);
+	size_t right = r_child (index);
+	size_t max_item = priority_queue->max_item;
+	
+	if (left < max_item && compare(priority_queue, left, index)) {
+		min = left;
+	}
+	
+	if (right < max_item && compare(priority_queue, right, min)) {
+		min = right;
+	}
+
+	if (min != index) {
+		swap_parent(priority_queue, min);
+		bubble_down(priority_queue, min);
+	}
+}
+
+void print_queue (PriorityQueue *priority_queue) {
+	for (int i = 0; i < priority_queue->size; i++) {
+		printf("%i\n", priority_queue->array[i]);
+	}
+}
+
+void swap_parent (PriorityQueue *priority_queue, size_t lower_index) {
+	int temp = priority_queue->array[lower_index];
+	priority_queue->array[lower_index] = priority_queue->array[parent(lower_index)];
+	priority_queue->array[parent(lower_index)] = temp;
+}
+
+bool compare (PriorityQueue *priority_queue, size_t first_index, size_t second_index) {
+	if (priority_queue->array[first_index] < priority_queue->array[second_index]) {
+		return true;
+	} else {
+		return false;
+	}
+}
diff --git a/priority_queue.h b/priority_queue.h
new file mode 100644
index 0000000..8422304
--- /dev/null
+++ b/priority_queue.h
@@ -0,0 +1,27 @@
+#include <stdbool.h>
+struct PriorityQueue {
+	int* array;
+	// The NEXT item to be added
+	size_t max_item;
+	size_t size;
+};
+
+typedef struct PriorityQueue PriorityQueue;
+
+void insert(PriorityQueue *priority_queue, int item);
+
+int extract (PriorityQueue *priority_queue);
+
+size_t parent (size_t index);
+size_t l_child (size_t index);
+size_t r_child (size_t index);
+
+void bubble_up (PriorityQueue *priority_queue, size_t index);
+
+void bubble_down (PriorityQueue *priority_queue, size_t index);
+
+void print_queue (PriorityQueue *priority_queue);
+
+void swap_parent (PriorityQueue *priority_queue, size_t lower_index);
+
+bool compare (PriorityQueue *priority_queue, size_t first_index, size_t second_index);