5 files changed, 255 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..47c0732
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+a.out
+linked_list_test*
+*.a
+*.o
+
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..9bf42df
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,16 @@
+CC=clang
+CFLAGS=-Wall -g
+BINS= linked_list.o liblinked_list.a linked_list_test
+all: $(BINS)
+
+linked_list.o: linked_list.h liblinked_list.c
+        $(CC) $(CFLAGS) -c liblinked_list.c
+
+liblinked_list.a: liblinked_list.o
+        ar -cvq liblinked_list.a liblinked_list.o
+
+linked_list_test: linked_list_test.c liblinked_list.a
+        $(CC) $(CFLAGS) -o $@ $^
+
+clean:
+        rm *.a *.o linked_list_test 
diff --git a/liblinked_list.c b/liblinked_list.c
new file mode 100644
index 0000000..83689a5
--- /dev/null
+++ b/liblinked_list.c
@@ -0,0 +1,179 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "linked_list.h"
+
+int count_ll(node* ptr){
+    /*
+    Count the number of nodes in a linked list.
+   */
+    // TODO:: What if there is 0 item in the linked list??
+    int count = 0;
+    while (ptr != NULL){
+        count++;
+        ptr = ptr->next;
+    }
+    return count;
+}
+
+void prepend_ll(node **ptr, int value){
+    /*
+    Add a node to the front of the linked list
+   */
+    node* new = malloc(sizeof(node));
+    new->value = value;
+    new->next = *ptr;
+    *ptr = new;
+
+}
+
+void append_ll(node* ptr, int value){
+    /*
+       Add a node to the end of the linked list
+   */
+    node* new = malloc(sizeof(node));
+    new->value = value;
+    new->next = NULL;
+    while (ptr->next != NULL){
+        ptr = ptr->next;
+    }
+    ptr->next = new;
+}
+
+void print_ll(node* ptr){
+    /*
+       Print out the linked list
+   */
+    while (ptr != NULL){
+        printf("%d", ptr->value);
+        ptr = ptr->next;
+        if (ptr == NULL){
+            break;
+        }
+        printf(" - ");
+    }
+    printf("\n");
+}
+
+void free_ll(node* ptr){
+    /*
+       Safely free all nodes inside linked list.
+   */
+    node* next;
+    while (ptr->next != NULL){
+        next = ptr->next;
+        free(ptr);
+        ptr = next;
+    }
+}
+
+int update_node(node* ptr, int index, int value){
+    /*
+       Update value of a node inside linked list
+   */
+    // TODO:: What if the index is out of range?
+
+    if (index >= count_ll(ptr)){
+        // index out of range
+        return 1;
+    }
+
+    int count = 0;
+    while (count < index){
+        ptr = ptr->next;
+        count++;
+    }
+
+    ptr->value = value;
+    return 0;
+}
+
+int delete_node(node **ptr, int index){
+    /*
+       Delete a node given the index
+   */
+
+    // TODO:: What if the node doesn't exist?
+    node* prev;
+    if (index == 0){
+        prev = *ptr;
+        *ptr = (*ptr)->next;
+        free(prev);
+        return 0;
+    }
+
+    node* root = *ptr;
+    for (int i = 0; i <= index; i++){
+        if (i == index){
+            prev->next = root->next;
+            free(root);
+            return 0;
+        }
+        prev = root;
+        root = root->next;
+    }
+    
+    printf("Node not found\n");
+    exit(-1);
+}
+
+int get_value(node *ptr, int index){
+    /*
+        Get the value of a specific node given the index
+   */
+    // TODO:: What if the index is out of range??
+
+    for (int i = 0; i < index; i++){
+        ptr = ptr->next;
+    }
+    return ptr->value;
+
+}
+
+node* search_node(node *ptr, int value){
+    /*
+        Search for a node given the value and returns it
+    */
+
+    while (1){
+        if (ptr == NULL){
+            fprintf(stderr, "Value doesn't exitst in linked list\n");
+            exit(-1);
+        }
+        if (ptr->value == value){
+            break;
+        }
+        ptr = ptr->next;
+    }
+    return ptr;
+}
+
+void reverse_ll(node** ptr){
+    node *prev, *cur, *next;
+    int n = count_ll(*ptr);
+
+    if (n == 0){
+        return;
+    }
+
+    if (n == 1){
+        return;
+    }
+    
+    prev = *ptr;
+    cur = prev->next; 
+    next = cur->next;
+    prev->next = NULL;
+
+    cur->next = prev;
+
+    for (int i = 0; i < n-2; i++){
+        prev = cur;
+        cur = next;
+        next = next->next;
+        cur->next = prev;
+    }
+
+
+    *ptr = cur;
+}
+
diff --git a/linked_list.h b/linked_list.h
new file mode 100644
index 0000000..1b2c3ca
--- /dev/null
+++ b/linked_list.h
@@ -0,0 +1,22 @@
+#ifndef __LINKED_LIST_H__
+#define __LINKED_LIST_H__
+
+typedef struct node node;
+struct node{
+    int value;
+    node* next;
+};
+
+int count_ll(node* ptr);
+void prepend_ll(node **ptr, int value);
+void append_ll(node* ptr, int value);
+void print_ll(node* ptr);
+void free_ll(node* ptr);
+int update_node(node* ptr, int index, int value);
+int delete_node(node **ptr, int index);
+int get_value(node *ptr, int index);
+node* search_node(node *ptr, int value);
+void reverse_ll(node **ptr);
+
+
+#endif
diff --git a/readme.md b/readme.md
new file mode 100644
index 0000000..c302e1b
--- /dev/null
+++ b/readme.md
@@ -0,0 +1,33 @@
+# Linked List in C
+This is a c library for linked list done as a learning project.
+
+The nodes stores integer values but can be switched to store any data you desire.
+
+Hopefully by viewing the source code you can learn how different operations on the linked list is implemented.
+
+# What has been implemented?
+
+First initialize your linked list like so:
+
+```c
+node* ll = malloc(sizeof(node));
+ll->value = 1;
+ll->next = NULL;
+```
+
+Then the following functions are available for you to interact with the linked list.
+
+These are the functions available in the header file.
+
+```c
+int count_ll(node* ptr);
+void prepend_ll(node **ptr, int value);
+void append_ll(node* ptr, int value);
+void print_ll(node* ptr);
+void free_ll(node* ptr);
+int update_node(node* ptr, int index, int value);
+int delete_node(node **ptr, int index);
+int get_value(node *ptr, int index);
+node* search_node(node *ptr, int value);
+void reverse_ll(node **ptr);
+```