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 : :
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/* 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 : :
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/* 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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