Created
August 28, 2012 10:46
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#include <stdio.h> | |
#include <stdlib.h> | |
struct bst | |
{ | |
struct bst *left,*right; | |
int val; | |
}; | |
struct bst* makenode(int); | |
struct bst* successor(struct bst*); | |
void insert(struct bst**,struct bst*); | |
void freetree(struct bst*); | |
void inorder(struct bst*); | |
int delete(struct bst**,int); | |
struct bst* search(struct bst*,int); | |
struct bst* findparent(struct bst*,struct bst*); | |
int main() | |
{ | |
struct bst* root=NULL; | |
int key,choice; | |
FILE *fp; | |
fp=fopen("input","r"); | |
fscanf(fp,"%d",&key); | |
while(!feof(fp)) | |
{ | |
struct bst* newnode=makenode(key); | |
insert(&root,newnode); | |
fscanf(fp,"%d",&key); | |
} | |
fclose(fp); | |
do | |
{ | |
printf("\nMENU\n1.INSERT\n2.DELETE\n3.INORDER\n4.EXIT"); | |
printf("\nENTER YOUR CHOICE(1/2/3/4):"); | |
scanf("%d",&choice); | |
switch(choice) | |
{ | |
case 1: printf("\nENTER KEY:"); | |
scanf("%d",&key); | |
insert(&root,makenode(key)); | |
printf("\nNEW NODE INSERTED"); | |
break; | |
case 2: printf("\nENTER KEY:"); | |
scanf("%d",&key); | |
int success=delete(&root,key); | |
if(success) | |
printf("\nNODE SUCCESSFULLY DELETED FROM TREE"); | |
else | |
printf("\nDELETION UNSUCCESSFUL"); | |
break; | |
case 3: inorder(root); | |
break; | |
case 4: freetree(root); | |
break; | |
default:printf("\nWRONG CHOICE"); | |
break; | |
} | |
} | |
while(choice!=4); | |
return 0; | |
} | |
void insert(struct bst** root,struct bst* newnode) | |
{ | |
if(*root==NULL) | |
*root=newnode; | |
else if((*root)->val>newnode->val) | |
insert(&((*root)->left),newnode); | |
else | |
insert(&((*root)->right),newnode); | |
} | |
void inorder(struct bst* root) | |
{ | |
if(root!=NULL) | |
{ | |
inorder(root->left); | |
printf("%d ",root->val); | |
inorder(root->right); | |
} | |
} | |
struct bst* successor(struct bst* node) | |
{ | |
if(node!=NULL) | |
node=node->right; | |
while(node!=NULL) | |
{ | |
if(node->left==NULL) | |
return node; | |
else | |
node=node->left; | |
} | |
return node; | |
} | |
struct bst* makenode(int key) | |
{ | |
struct bst* newnode=malloc(sizeof(struct bst)); | |
newnode->val=key; | |
newnode->left=newnode->right=NULL; | |
return newnode; | |
} | |
void freetree(struct bst* root) | |
{ | |
if(root!=NULL) | |
{ | |
freetree(root->left); | |
freetree(root->right); | |
free(root); | |
} | |
} | |
struct bst* search(struct bst *root,int key) | |
{ | |
if(root!=NULL) | |
{ | |
if(root->val==key) | |
return root; | |
else if(root->val>key) | |
return(search(root->left,key)); | |
else | |
return(search(root->right,key)); | |
} | |
else | |
return root; | |
} | |
struct bst* findparent(struct bst* root,struct bst* temp) | |
{ | |
if(root==temp) | |
return NULL; | |
while(root!=NULL) | |
{ | |
if(root->val>temp->val) | |
{ | |
if(root->left!=NULL) | |
{ | |
if(root->left->val==temp->val) | |
return root; | |
root=root->left; | |
} | |
} | |
else | |
{ | |
if(root->right!=NULL) | |
{ | |
if(root->right->val==temp->val) | |
return root; | |
root=root->right; | |
} | |
} | |
} | |
return NULL; | |
} | |
int delete(struct bst** root,int key) | |
{ | |
struct bst *find=search(*root,key); | |
if(find==NULL) | |
return 0; | |
else | |
{ | |
if(find->left==NULL&&find->right==NULL) | |
{ | |
if(find==*root) | |
free(find); | |
else | |
{ | |
struct bst *parent=findparent(*root,find); | |
if(parent->left!=NULL) | |
if(parent->left==find) | |
parent->left=NULL; | |
if(parent->right!=NULL) | |
if(parent->right==find) | |
parent->right=NULL; | |
free(find); | |
} | |
} | |
else if(find->left!=NULL&&find->right==NULL) | |
{ | |
struct bst* save=find->left; | |
find->val=find->left->val; | |
find->right=find->left->right; | |
find->left=find->left->left; | |
free(save); | |
} | |
else if(find->right!=NULL&&find->left==NULL) | |
{ | |
struct bst* save=find->right; | |
find->val=find->right->val; | |
find->left=find->right->left; | |
find->right=find->right->right; | |
free(save); | |
} | |
else | |
{ | |
struct bst* heir=successor(find); | |
int key=heir->val; | |
if(delete(root,key)) | |
find->val=key; | |
} | |
} | |
return 1; | |
} |
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For deleting nodes with two children the logic that a successor will not have a left child is used
save successors key, delete successor using the same function, copy successors value to the node to be deleted