added singly linked list in C

algorithms/C/linked-lists/singly-linked-list.c

@@ -0,0 +1,268 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+//structure mimic the link node
+struct node{
+    int data;
+    struct node* next;
+};
+
+typedef struct node Node;
+
+Node *head = NULL;
+int count = 0;
+
+void insertAtBegin(int x);
+void insertAtEnd(int x);
+void insertAtBefore(int x, int before);
+void insertAtAfter(int x, int after);
+int length();
+void display();
+void deleteAtBegin();
+void deleteAtEnd();
+void deleteAtAfter(int after);
+void deleteAtBefore(int before);
+void search(int key);
+
+int main()
+{    
+    insertAtEnd(40);
+    printf("The no of nodes in the list is %d\n", length());
+    insertAtBegin(10);
+    insertAtBegin(20);
+    display();
+    printf("The no of nodes in the list is %d\n", length());
+    insertAtBegin(30);
+    insertAtEnd(50);
+    insertAtAfter(60, 10);
+    insertAtBefore(70, 10);
+    display();
+    printf("The no of nodes in the list is %d\n", length());
+    search(30);
+    search(10);
+    search(50);
+    printf("The no of nodes in the list is %d\n", length());
+    deleteAtBegin();
+    display();
+    deleteAtEnd();
+    display();
+    deleteAtAfter(60);
+    display();
+    deleteAtBefore(10);
+    display();
+}
+
+void display()
+{
+    if (head == NULL)
+    {
+        printf("The linked list is empty\n");
+        return;
+    }
+    Node *temp = head;
+    while (temp != NULL)
+    {
+        printf("%d --> ", temp->data);
+        temp = temp->next;
+    }
+    printf("NULL\n");
+}
+
+int length()
+{
+    if (head == NULL)
+    {
+        return -1;
+    }
+    Node *temp = head;
+    int count = 0;
+    while (temp != NULL)
+    {
+        count++;
+        temp = temp->next;
+    }
+    return count;
+}
+
+void insertAtBegin(int x)
+{
+    Node *newNode = (Node *)malloc(sizeof(Node));
+    if (newNode == NULL)
+    {
+        printf("OVERFLOW\n");
+        return;
+    }
+    newNode->data = x;
+    newNode->next = NULL;
+    if (head == NULL)
+    {
+        head = newNode;
+    }
+    else
+    {
+        newNode->next = head;
+        head = newNode;
+    }
+}
+
+void insertAtEnd(int x)
+{
+    Node *newNode = (Node *)malloc(sizeof(Node));
+    if (newNode == NULL)
+    {
+        printf("OVERFLOW\n");
+        return;
+    }
+    newNode->data = x;
+    newNode->next = NULL;
+    //check if the list is empty and if it is then insert the node at the beginning
+    if (head == NULL)
+    {
+        head = newNode;
+    }
+    else
+    {
+        Node *temp = head;
+        while (temp->next != NULL)
+        {
+            temp = temp->next;
+        }
+        temp->next = newNode;
+    }
+}
+
+//assumes after value already exists in the list
+void insertAtAfter(int x, int after)
+{
+    Node *newNode = (Node *)malloc(sizeof(Node));
+    if (newNode == NULL)
+    {
+        printf("OVERFLOW\n");
+        return;
+    }
+    newNode->data = x;
+    newNode->next = NULL;
+
+    Node *temp = head;
+    while (temp->data != after)
+    {
+        temp = temp->next;
+    }
+    newNode->next = temp->next;
+    temp->next = newNode;
+}
+
+//assumes before value already exist in the list
+void insertAtBefore(int x, int before)
+{
+    Node *newNode = (Node *)malloc(sizeof(Node));
+    if (newNode == NULL)
+    {
+        printf("OVERFLOW\n");
+        return;
+    }
+    newNode->data = x;
+    newNode->next = NULL;
+
+    Node *temp = head;
+    while (temp->next->data != before)
+    {
+        temp = temp->next;
+    }
+    newNode->next = temp->next;
+    temp->next = newNode;
+}
+
+void deleteAtBegin()
+{
+    if (head == NULL)
+    {
+        printf("UNDERFLOW\n");
+        return;
+    }
+    Node *temp = head;
+    printf("The value deleted is %d \n", temp->data);
+    head = temp->next;
+    temp->next = NULL;
+    free(temp);
+}
+
+void deleteAtEnd()
+{
+    if (head == NULL)
+    {
+        printf("UNDERFLOW\n");
+        return;
+    }
+    Node *temp = head, *p;
+    while (temp->next->next != NULL)
+    {
+        temp = temp->next;
+    }
+    p = temp->next;
+    printf("The value deleted is %d \n", p->data);
+    temp->next = NULL;
+    free(p);
+}
+
+void deleteAtAfter(int after)
+{
+    if (head == NULL)
+    {
+        printf("UNDERFLOW\n");
+        return;
+    }
+    Node *temp = head, *p;
+    while (temp->data != after)
+    {
+        temp = temp->next;
+    }
+    p = temp->next;
+    printf("The value deleted is %d \n", p->data);
+    temp->next = p->next;
+    free(p);
+}
+
+void deleteAtBefore(int before)
+{
+    if (head == NULL)
+    {
+        printf("UNDERFLOW\n");
+        return;
+    }
+    Node *temp = head, *p;
+    while (temp->next->next->data != before)
+    {
+        temp = temp->next;
+    }
+    p = temp->next;
+    printf("The value deleted is %d \n", p->data);
+    temp->next = p->next;
+    free(p);
+}
+
+void search(int key)
+{
+    if (head == NULL)
+    {
+        printf("UNDERFLOW\n");
+        return;
+    }
+    int count = 1; // counting starts from 1
+    Node *temp = head;
+    while (temp->data != key)
+    {
+        temp = temp->next;
+        count++;
+    }
+    if (count <= length())
+    {
+        printf("The node number %d has the value %d\n", count, key);
+    }
+    else
+    {
+        printf("The value %d is not found in the list\n");
+    }
+}
+
+