Single linked list

Linked List/singleLinkedList.c

@@ -0,0 +1,198 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+//creating a structure node 
+struct node{
+    int key;
+    struct node *addr;
+};
+
+struct node *front=NULL;
+struct node *rear=NULL;
+
+//Function to display the linked list items in order
+void display(){
+    struct node *temp2;
+    temp2 = front;
+    while(temp2!=NULL){
+        printf("%d\t",temp2->key);
+        temp2=temp2->addr;
+    }
+}
+
+//Function to display the linked list items in reverse order
+void display_r(){
+    int i,j,k;
+    struct node *temp,*temp2;
+    i=0;
+    temp2=front;
+    while(temp2!=NULL){
+        i++;
+        temp2=temp2->addr;
+    }
+    j=i;
+    for(k=j;k>1;k--){
+        temp=front;
+        i=0;
+        do{
+            temp=temp->addr;
+            i++;
+        }while(i<k-1);
+        printf("%d\t", temp->key);
+    }
+    printf("%d",front->key);
+}
+
+//Function to insert element at beginning of linked list
+void insert_at_begin(int key1){
+    struct node *temp=(struct node*)malloc(sizeof(struct node));
+    if(front==NULL){
+        front=rear=temp;
+        temp->key=key1;
+        temp->addr=NULL;
+    }
+    else{
+        temp->addr=front;
+        temp->key=key1;
+        front=temp;
+    }
+}
+
+//Function to insert element at th end of linked list
+void insert_at_end(int key1){
+    struct node *temp=(struct node*)malloc(sizeof(struct node));
+    if(front==NULL || rear==NULL) {
+        temp->key=key1;
+        temp->addr=NULL;
+        front=temp;
+        rear=temp;
+    }
+    else {
+        rear->addr=temp;
+        temp->key=key1;
+        temp->addr=NULL;
+        rear=temp;
+    }
+}
+
+//Function to insert the element at some position of the linked list
+void insert_at_pos(int key1,int pos){
+    struct node *temp=(struct node*)malloc(sizeof(struct node));
+    struct node *temp1;
+    int i;
+    temp->key=key1;
+    temp1=front;
+    if(front==NULL || rear==NULL) {
+        front=temp;
+        rear=temp;
+    }
+    else {
+        for(i=0;i<pos-1;i++){
+            temp1=temp1->addr;
+        }
+        temp->addr=temp1->addr;
+        temp1->addr=temp;
+    }
+}
+
+//Function to delete element at beginning of linked list
+void delete_at_begin(){
+    if(front==NULL && rear==NULL){
+        printf("list is empty");
+    }
+    else if(front==rear){
+        free(front);
+        front=rear=NULL;
+    }
+    else{
+        struct node*temp;
+        temp=front->addr;
+        front=temp;
+    }
+}
+
+//Function to delete element at the end of linked list
+void delete_at_end()
+{
+    struct node*temp;
+    if(front==NULL){
+        printf("list is empty");
+    }
+    else{
+    temp=front;
+    while(temp->addr!=rear){
+        temp=temp->addr;
+    }
+    printf("deleted element is  %d",rear->key);
+    temp->addr=NULL;
+    rear=temp;
+    }
+}
+
+//Function to delete element at some position of linked list
+void delete_at_pos(int pos){
+    struct node *temp,*temp1;
+    int i;
+    if(front==NULL){
+        printf("list is empty");
+    }
+    else if(front==rear){
+        printf("deleted element is\t%d",front->key);
+        front=NULL;
+        rear=NULL;
+    }
+    else{
+    temp1=front;
+    for(i=1;i<pos;i++){
+        temp1=temp1->addr;
+    }
+    temp=temp1->addr;
+    temp1->addr=temp->addr;
+    temp->addr=NULL;
+    free(temp);
+    }
+}
+int main(){
+    int n,n1,key1,pos,pos1,n2;
+    do{
+        printf("\nselect an option:1.Insert\t2.delete\t3.display\t4.display reverse\t5.exit");
+        scanf("%d",&n);
+        switch(n){
+            case 1: printf("\nenter element");
+                    scanf("%d",&key1);
+                    printf("\nselect where to insert?:1.begin\t2.end\t3.pos");
+                    scanf("%d",&n1);
+                //Switch case to choose inserting (or) deleting (or) displaying element in linked list
+                    switch(n1){
+                        case 1: insert_at_begin(key1);
+                                break;
+                        case 2: insert_at_end(key1);
+                                break;
+                        case 3: printf("\nenter position to insert?:");
+                                scanf("%d",&pos);
+                                insert_at_pos(key1,pos);
+                                break;
+                    }
+                    break;
+            case 2: printf("\nselect option where to delete?:1.begin\t2.end\t3.pos");
+                    scanf("%d",&n2);
+                    switch(n2){
+                        case 1: delete_at_begin();
+                                break;
+                        case 2: delete_at_end();
+                                break;
+                        case 3: printf("\nenter position where to delete");
+                                scanf("%d",&pos1);
+                                delete_at_pos(pos1);
+                                break;
+                    }
+                    break;
+            case 3: display();
+                    break;
+            case 4: display_r();
+                    break;
+            case 5: exit(0);
+            default : printf("\nselect valid option");
+        }
+    }while(1);
+}