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Monday, December 23, 2013

postorder traversal using stack

postorder traversal
here the c code for postorder traversal using stack.

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#include<stdio.h>
#include<stdlib.h>
struct node
{
 int data;
 struct node *LCHILD;
 struct node *RCHILD;
}*tree;
struct stack
{
 struct node *addr[100];
 int top;
}s,s1,s2;
void push(struct node *val,struct stack *temp)
{
 if(temp->top==99)
 {
  printf("overflow\n");
  return ;
 }
 temp->addr[++temp->top]=val;
}
struct node *pop(struct stack *temp)
{
 if(temp->top==-1)
 {
  printf("under flow\n");
  return NULL;
 }
 return temp->addr[temp->top--];
}
struct node *peep(struct stack * temp)
{
 if(temp->top==-1)
  return NULL;
 return temp->addr[temp->top];
}
struct node *create(int val)
{
 struct node *temp;
 temp=(struct node*)malloc(sizeof(struct node));
 temp->data=val;
 temp->LCHILD=NULL;
 temp->RCHILD=NULL;
 return temp;
}
void add(struct node **tr,int val)
{
 struct node *copy,*copy1;
 copy=(struct node*)malloc(sizeof(struct node));
 copy1=(struct node*)malloc(sizeof(struct node));
 copy1=*tr;
 if(copy1==NULL)
 {
  *tr=create(val);
  return ;
 }
 if(val>=copy1->data)
  add(&(copy1->RCHILD),val);
 else
  add(&(copy1->LCHILD),val);
}
void print_postorder(struct node *root)
{
 if(root==NULL)
  return;
 do
 {
  while(root!=NULL)
  {
   if(root->RCHILD!=NULL)
    push(root->RCHILD,&s2);
   push(root,&s2);
   root=root->LCHILD;
  }
  root=pop(&s2);
  if(root->RCHILD!=NULL && root->RCHILD==peep(&s2))
  {
   pop(&s2);
   push(root,&s2);
   root=root->RCHILD;
  }
  else
  {
   printf("%d\t",root->data);
   root=NULL;
  }
 }while(s2.top!=-1);
}
int main()
{
 tree=NULL;
 s.top=-1;
 s1.top=-1;
 s2.top=-1;
REPEAT:
 printf("ENTER YOUR CHOICE\n");
 printf("1->add node to tree\n");
 printf("2->print in INORDER tree\n");
        printf("3->exit\n");
 int choice,val;
 scanf("%d",&choice);
 switch(choice)
 {
 case 1:
  scanf("%d",&val);
  add(&tree,val);
  break;
 case 2:
  print_postorder(tree);
  break;
 case 3:
  exit(2);
 default:
  printf("your choice is incorrect\n");
 }
 goto REPEAT;
 return 0;
}