Create queue_using_linked_list.c

algorithms/C/queues/queue_using_linked_list.c

@@ -0,0 +1,93 @@
+#include <stdio.h>
+#include <stdlib.h>
+struct node *enqueue(struct node*);
+struct node *dequeue(struct node*);
+void display(struct node*);
+void peek(struct node*);
+struct node{
+    int data;
+    struct node *next;
+};
+
+int main(){
+    struct node *front=0,*rear=0;
+    int choice;
+    printf("Press 1 for Enqueue\nPress 2 for Dequeue\nPress 3 for Display\nPress 4 for Peek\nPress 5 for Exit\n");
+    do{
+        printf("\nEnter the choice: ");
+        scanf("%d",&choice);
+        switch(choice){
+            case 1: rear=enqueue(rear);
+            if(front==0){
+                front=rear;
+            }
+            break;
+
+            case 2: if(front==0 && rear==0){
+                printf("Queue is Empty");
+                break;
+            }
+            else{
+                front=dequeue(front);
+                if(front==0){
+                    rear=0;
+                }
+                break;
+            }
+
+            case 3: if(front==0){
+                printf("Queue is Empty");
+                break;
+            }
+            else{
+                display(front);
+                break;
+            }
+
+            case 4: if(front==0){
+                printf("Queue is Empty");
+                break;
+            }
+            else{
+                peek(front);
+                break;
+            }
+
+            case 5: break;
+            default: printf("Invalid Choice");
+        }
+    }while(choice!=5);
+}
+struct node *enqueue(struct node *rear){
+    struct node *newnode;
+    newnode=(struct node*)malloc(sizeof(struct node));
+    printf("Enter the data: ");
+    scanf("%d",&newnode->data);
+    newnode->next=0;
+    if(rear==0){
+        rear=newnode;
+    }
+    else{
+        rear->next=newnode;
+        rear=newnode;
+        return rear;
+    }
+}
+struct node *dequeue(struct node *front){
+    struct node*temp=front;
+    printf("The enqueued element is %d",front->data);
+    front=front->next;
+    free(temp);
+    return front;
+}
+void display(struct node *front){
+    struct node *temp=front;
+    printf("The elements in the queue are: ");
+    while(temp!=0){
+        printf("%d ",temp->data);
+        temp=temp->next;
+    }
+}
+void peek(struct node *front){
+    printf("The Peek element is %d",front->data);
+}