Merge branch 'main' of github.com:ergz/tlacyl

c/linked_list.c

@@ -3,25 +3,25 @@
 
 typedef struct Node {
     int          value;
-    struct Node* next;
-    struct Node* prev;
+    struct Node *next;
+    struct Node *prev;
 } Node;
 
 typedef struct LinkedList {
     int   length;
-    Node* head;
-    Node* tail;
+    Node *head;
+    Node *tail;
 } LinkedList;
 
-LinkedList* new_linked_list() {
-    LinkedList* ll = malloc(sizeof(LinkedList));
+LinkedList *new_linked_list() {
+    LinkedList *ll = malloc(sizeof(LinkedList));
     ll->length = 0;
 
     return (ll);
 }
 
-Node* new_node(int value) {
-    Node* n = malloc(sizeof(Node));
+Node *new_node(int value) {
+    Node *n = malloc(sizeof(Node));
     n->value = value;
     n->next = NULL;
     n->prev = NULL;
@@ -29,7 +29,7 @@ Node* new_node(int value) {
 }
 
 // append - insert a node at the end of the linked list
-void append(LinkedList* list, Node* n) {
+void append(LinkedList *list, Node *n) {
     if (list->length == 0) {
         list->head = n;
         list->tail = n;
@@ -43,7 +43,7 @@ void append(LinkedList* list, Node* n) {
 }
 
 // prepend - insert a node at the front of the linked list
-void preppend(LinkedList* list, Node* node) {
+void preppend(LinkedList *list, Node *node) {
     if (list->length == 0) {
         list->head = node;
         list->tail = node;
@@ -58,7 +58,7 @@ void preppend(LinkedList* list, Node* node) {
 }
 
 // insert at - insert a node at a given index
-void insert_at(LinkedList* list, Node* node, int index) {
+void insert_at(LinkedList *list, Node *node, int index) {
     if (index == 0) {
         preppend(list, node);
     } else if (index == list->length) {
@@ -66,7 +66,7 @@ void insert_at(LinkedList* list, Node* node, int index) {
     } else if (index > list->length || index < 0) {
         printf("ERROR: cannot add to list at index position %d, this is beyond the current index\n", index);
     } else {
-        Node* current_node_at_index = list->head;
+        Node *current_node_at_index = list->head;
         // get to the ith node
         for (int i = 0; i < index; i++) {
             current_node_at_index = current_node_at_index->next;
@@ -91,16 +91,17 @@ void remove_at_end(LinkedList* list) {
     }
 }
 
-int get_length(LinkedList* list) {
+
+int get_length(LinkedList *list) {
     return (list->length);
 }
 
-void destroy_list(LinkedList* list) {
+void destroy_list(LinkedList *list) {
     // if any nodes are in list destroy them first
     if (list->length > 0) {
-        Node* current_node = list->head;
+        Node *current_node = list->head;
         while (current_node != NULL) {
-            Node* next_node = current_node->next;
+            Node *next_node = current_node->next;
             free(current_node);
             current_node = next_node;
         }
@@ -110,8 +111,8 @@ void destroy_list(LinkedList* list) {
     free(list);
 }
 
-void print_list(LinkedList* list) {
-    Node* curr = list->head;
+void print_list(LinkedList *list) {
+    Node *curr = list->head;
     printf("[ ");
     while (curr != NULL) {
         printf("%d ", curr->value);
@@ -187,3 +188,4 @@ int main() {
 
     return (0);
 }
+

c/qs.c

@@ -5,9 +5,9 @@
 // of it and everything greater than it on the right
 int partition(int arr[], int lo, int hi) {
     int pivot_value = arr[hi];
-    int idx = -1;  // this will keep track of current location of values less then the pivot
+    int idx = lo - 1;  // this will keep track of current location of values less then the pivot
 
-    for (int i = 0; i < hi; i++) {
+    for (int i = lo; i < hi; i++) {
         if (arr[i] <= pivot_value) {
             idx++;
 

c/qs2.cpp

@@ -0,0 +1,69 @@
+#include <stdio.h>
+
+/* a rewrite to make sure I can do this without reading */
+
+/*
+partition
+
+Modifies array by moving all values less then a pivot point
+to the left of it and all value greater to the right. Returns
+the index of the pivot at the end of the process.
+
+@param int arr[] array to partition
+@param int lo low value to start iteration on
+@param int hi high value to end iteration on
+ */
+int partition(int arr[], int lo, int hi) {
+    int pindex = lo - 1;        // where pivot will end up
+    int pivot_value = arr[hi];  // can be different
+
+    for (int i = lo; i < hi; i++) {
+        if (arr[i] <= pivot_value) {
+            pindex++;
+            int temp = arr[i];
+            arr[i] = arr[pindex];
+            arr[pindex] = temp;
+        }
+    }
+
+    // after iterating through array, we place pivot in correct
+    // position
+    pindex++;
+    arr[hi] = arr[pindex];
+    arr[pindex] = pivot_value;
+
+    return (pindex);
+}
+
+/*
+quick_sort
+
+@param int arr[] array to be sorted
+@param int lo starting point for iteration
+@param int hi ending point for itereation
+ */
+void quick_sort(int arr[], int lo, int hi) {
+    if (lo < hi) {  // base case is lo == hi
+        int pivot_index = partition(arr, lo, hi);
+
+        quick_sort(arr, lo, pivot_index - 1);
+        quick_sort(arr, pivot_index + 1, hi);
+    }
+}
+
+void print_array(int arr[], int len) {
+    printf("[ ");
+    for (int i = 0; i < len; i++) {
+        printf("%d ", arr[i]);
+    }
+    printf("]\n");
+}
+
+int main() {
+    int arr[5] = {5, 4, 3, 2, 1};
+    printf("before ");
+    print_array(arr, 5);
+    quick_sort(arr, 0, 4);
+    printf("after ");
+    print_array(arr, 5);
+}