Construct tree from inorder and postorder
Write a C Program to construct binary tree from inorder and postorder. Here’s simple Program to construct binary tree from inorder and postorder in C Programming Language.
What is Tree ?
In linear data structure, data is organized in sequential order and in non-linear data structure, data is organized in random order. Tree is a very popular data structure used in wide range of applications.
A tree data structure can be defined as follows…
- Tree is a non-linear data structure which organizes data in hierarchical structure and this is a recursive definition.
A tree data structure can also be defined as follows…
- Tree data structure is a collection of data (Node) which is organized in hierarchical structure and this is a recursive definition.
Every individual element is called as Node. Node in a tree data structure, stores the actual data of that particular element and link to next element in hierarchical structure.
Below is the source code for C Program to construct binary tree from inorder and postorder which is successfully compiled and run on Windows System to produce desired output as shown below :
SOURCE CODE : :
/* C Program to construct binary tree from inorder and postorder */
#include<stdio.h>
#include<stdlib.h>
struct treenode
{
int info;
struct treenode *lchild;
struct treenode *rchild;
}*root=NULL;
struct listnode
{
struct listnode *prev;
int info;
struct listnode *next;
}*post=NULL, *in=NULL;
void display(struct treenode *ptr,int level);
struct listnode *addtoempty(struct listnode *start,int data);
struct listnode *addatend(struct listnode *start,int data);
struct listnode *create_list(struct listnode *start, int n);
struct treenode *construct(struct listnode *inptr,struct listnode *postptr, int num);
void inorder(struct treenode *ptr);
void preorder(struct treenode *ptr);
void postorder(struct treenode *ptr);
int main()
{
int n;
printf("Enter the number of nodes : ");
scanf("%d",&n);
printf("\nEnter inorder :\n");
in = create_list(in,n);
printf("\nEnter postorder:\n");
post = create_list(post,n);
root = construct(in,post,n);
printf("\nInorder : "); inorder(root);
printf("\n\nPostorder : "); postorder(root);
printf("\n\nPreorder : "); preorder(root);
printf("\n\n\nTree is : \n");
display(root,0);
printf("\n");
return 0;
}/*End of main()*/
struct treenode *construct(struct listnode *inptr,struct listnode *postptr, int num)
{
struct treenode *temp;
struct listnode *q, *ptr;
int i,j;
if(num==0)
return NULL;
ptr=postptr;
for(i=1;i<num;i++)
ptr = ptr->next;
/*Now ptr points to last node of postorder which is root*/
temp=(struct treenode *)malloc(sizeof(struct treenode));
temp->info=ptr->info;
temp->lchild = NULL;
temp->rchild = NULL;
if(num==1)/*if only one node in tree */
return temp;
q=inptr;
for(i=0; q->info!=ptr->info; i++ )
q = q->next;
/*Now i denotes the number of nodes in left subtree
and q points to root node in inorder list*/
/*For left subtree*/
temp->lchild = construct(inptr, postptr, i);
/*For right subtree*/
for(j=1;j<=i;j++)
postptr = postptr->next;
temp->rchild = construct(q->next, postptr, num-i-1);
return temp;
}/*End of construct()*/
struct listnode *create_list(struct listnode *start, int n)
{
int i,data;
start=NULL;
for(i=1;i<=n;i++)
{
printf("Enter the element to be inserted : ");
scanf("%d",&data);
if(start==NULL)
start=addtoempty(start,data);
else
start=addatend(start,data);
}
return start;
}/*End of create_list()*/
struct listnode *addtoempty(struct listnode *start,int data)
{
struct listnode *tmp;
tmp=(struct listnode*)malloc(sizeof(struct listnode));
tmp->info=data;
tmp->prev=NULL;
tmp->next=NULL;
start=tmp;
return start;
}/*End of addtoempty( )*/
struct listnode *addatend(struct listnode *start,int data)
{
struct listnode *tmp,*p;
tmp=(struct listnode*)malloc(sizeof(struct listnode));
tmp->info=data;
p=start;
while(p->next!=NULL)
p=p->next;
p->next=tmp;
tmp->next=NULL;
tmp->prev=p;
return start;
}/*End of addatend( )*/
void inorder(struct treenode *ptr)
{
if(root==NULL)
{
printf("Tree is empty");
return;
}
if(ptr!=NULL)
{
inorder(ptr->lchild);
printf("%d ",ptr->info);
inorder(ptr->rchild);
}
}/*End of inorder( )*/
void postorder(struct treenode *ptr)
{
if(root==NULL)
{
printf("Tree is empty");
return;
}
if(ptr!=NULL)
{
postorder(ptr->lchild);
postorder(ptr->rchild);
printf("%d ",ptr->info);
}
}/*End of postorder( )*/
void preorder(struct treenode *ptr)
{
if(root==NULL)
{
printf("Tree is empty");
return;
}
if(ptr!=NULL)
{
printf("%d ",ptr->info);
preorder(ptr->lchild);
preorder(ptr->rchild);
}
}/*End of preorder( )*/
void display(struct treenode *ptr,int level)
{
int i;
if(ptr!=NULL)
{
display(ptr->rchild, level+1);
printf("\n");
for (i = 0; i < level; i++)
printf(" ");
printf("%d", ptr->info);
display(ptr->lchild, level+1);
}
}/*End of display()*/
OUTPUT : :
/* C Program to construct binary tree from inorder and postorder */
Enter the number of nodes : 7
Enter inorder :
Enter the element to be inserted : 1
Enter the element to be inserted : 2
Enter the element to be inserted : 3
Enter the element to be inserted : 4
Enter the element to be inserted : 5
Enter the element to be inserted : 6
Enter the element to be inserted : 7
Enter postorder:
Enter the element to be inserted : 7
Enter the element to be inserted : 6
Enter the element to be inserted : 5
Enter the element to be inserted : 4
Enter the element to be inserted : 3
Enter the element to be inserted : 2
Enter the element to be inserted : 1
Inorder : 1 2 3 4 5 6 7
Postorder : 7 6 5 4 3 2 1
Preorder : 1 2 3 4 5 6 7
Tree is :
7
6
5
4
3
2
1
Process returned 0
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