Create AscendingPriorityQueue.c

shubhamsah · web-flow · commit 8ac3f2a609d2 · 2020-05-23T21:28:16.000+05:30
diff --git a/data_structures/linked_list/APQ.C b/data_structures/linked_list/APQ.C
@@ -0,0 +1,169 @@
+/* Ascending priority queue using Linked List - Program to implement Ascending priority queue using Linked List */
+
+#include  <stdio.h>
+#include  <stdlib.h>  
+#define  NULL  0
+
+struct  node
+{
+  int  data ;
+  struct  node  *next ;
+} ;
+
+struct  node  *front , *rear ;
+
+/* This function initializes the queue to empty by making both front and rear as NULL */
+void createqueue()
+{
+  front=rear=NULL ;
+}
+
+int  empty()
+{
+  if(front==NULL)
+    return  1 ;
+  else
+    return  0 ;
+}
+
+void  insert(int  x)
+{
+  struct  node  *pnode ;
+
+  pnode=(struct node*)malloc(sizeof(struct node)) ;
+  if(pnode==NULL)
+  {
+    printf("Memory overflow. Unable to insert.\n") ;
+    getch();
+    exit(1) ;
+  }
+
+  pnode->data=x ;  
+  pnode->next=NULL;   /* New node is always last node */
+
+  if(empty())
+      front=rear=pnode ;
+  else
+  {
+      rear->next=pnode ;
+      rear=pnode ;
+  }
+}
+
+int  removes()
+{
+  int  min ;
+  struct  node  *follow , *follow1 , *p , *p1 ;
+
+  if(empty())
+  {
+    printf("\nQueue Underflow. Unable to remove.") ;
+    getch() ;
+    exit(1) ;
+  }
+
+  /* finding the node with minimum value in the APQ.*/
+  p=p1=front ;
+  follow=follow1=NULL ;
+  min=front->data ;
+  while(p!=NULL)
+  {
+    if(p->data<min)
+    {
+   min=p->data ;
+   follow1=follow ;
+   p1=p ;
+    }
+    follow=p ;
+    p=p->next ;
+  }
+
+  /* Deleting the node with min value */
+
+  if(p1==front)  /* deleting first node.*/
+  {
+    front=front->next ;
+    if(front==NULL)  /* Deleting the only one node */
+      rear=NULL ;
+  }
+  else if(p1==rear)  /* Deleting last node */
+  {
+      rear=follow1 ;
+      rear->next=NULL ;
+  }
+  else      /* deleting any other node.*/
+      follow1->next=p1->next ;
+
+
+  free(p1) ;
+  return  min ;  /* DONT FORGET LAST 2 STATEMENTS.*/
+}
+
+void  show()
+{
+  struct  node  *p ;
+
+  if(empty())
+    printf("Queue empty. No data to display \n") ;
+  else
+  {
+    printf("Queue from front to rear is as shown: \n") ;
+
+    p=front ;
+    while(p!=NULL)
+    {
+      printf("%d ",p->data) ;
+      p=p->next ;
+    }
+
+    printf("\n") ;
+  }
+}
+
+void  destroyqueue()
+{
+  front=rear=NULL ;
+}
+
+int  main()
+{
+  int  x , ch ;
+
+  createqueue() ;
+
+
+  do
+  {
+    printf("\n\n  Menu: \n") ;
+    printf("1:Insert \n") ;
+    printf("2:Remove \n") ;
+    printf("3:exit \n") ;
+    printf("Enter your choice: ") ;
+    scanf("%d",&ch) ;
+
+    switch(ch)
+    {
+      case 1:
+      printf("Enter element to be inserted: ") ;
+      scanf("%d",&x) ;
+      insert(x) ;
+      show() ;
+      break ;
+
+      case 2:
+      x=removes() ;
+      printf("Element removed is: %d\n",x) ;
+      show() ;
+      break ;
+
+      case 3:
+      break ;
+    }
+  }
+  while(ch!=3) ;
+
+  destroyqueue() ;
+
+  return 0;
+}
+
