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huffman coding
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huffman coding
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#include<stdio.h>
#include<stdlib.h>
#include<string.h>
static int size=0;
char decode[26][100];
typedef struct element{
char ch;
int frequency;
struct element* left;
struct element* right;
}element;
void swap(element* arr,int i,int j){
element temp=arr[i];
arr[i]=arr[j];
arr[j]=temp;
}
void display(element* array){
if(array->left==NULL)
{
printf("In display : %c %d\n",array->ch,array->frequency);
return;
}
else{
display(array->left);
display(array->right);;
}
}
void heapify(element* array,int pos){
//0-based indexing
int left=2*pos+1;
int right=2*pos+2;
int smallest=pos;
if(left<size && array[left].frequency <= array[smallest].frequency) smallest=left;
if(right<size && array[right].frequency <= array[smallest].frequency) smallest=right;
if(smallest!=pos){
swap(array,smallest,pos);
heapify(array,smallest);
}
}
void deletefun(element* array){
swap(array,0,size-1);
size--;
int i;
//should be heapified top to bottom
for(i=0;i<=size/2-1;i++) heapify(array,i);
}
element minEle(element* array){
element temp;
temp.frequency=array[0].frequency;
temp.ch=array[0].ch;
temp.right=array[0].right;temp.left=array[0].left;
deletefun(array);
return temp;
}
void insert(element* array,element ele){
array[size++]=ele;
int i;
for(i=size/2-1;i>=0;i--) heapify(array,i);
}
void print(element* arr,int n){
int i;
for(i=0;i<n;i++) printf("%c %d\n",arr[i].ch,arr[i].frequency);
printf("\n");
}
int height(element *arr){
if(arr->left==NULL||arr->right==NULL)
return 1;
int left=1+height(arr->left);
int right=1+height(arr->right);
return left>right?left:right;
}
void HuffmanEncoding(element* array){
element first_min;
element second_min;
while(size > 1){
first_min=minEle(array);
second_min=minEle(array);
/*
if first_min->frequency is greater than that of second_min->frequency ,then first_min is inserted at the right of the new element
*/
element temp;
temp.ch='\0';
//display(&first_min);
//display(&second_min);
if(first_min.left!=NULL) printf("Left's left is %d %c\n",first_min.left->frequency,first_min.left->ch);
if(first_min.right!=NULL) printf("left's right is %d %c\n",first_min.right->frequency,first_min.right->ch);
if(second_min.left!=NULL) printf("right's left is %d %c\n",second_min.left->frequency,second_min.left->ch);
if(second_min.right!=NULL) printf("right's right is %d %c\n",second_min.right->frequency,second_min.right->ch);
if(second_min.right!=NULL && second_min.right->ch=='\0') printf("Internal left is %c right is %c\n",second_min.right->left->ch,second_min.right->right->ch);
temp.frequency=first_min.frequency+second_min.frequency;
if(first_min.frequency > second_min.frequency)
{
temp.left=&second_min;
temp.right=&first_min;
insert(array,temp);
}
else{
temp.left=&first_min;
temp.right=&second_min;
insert(array,temp);
}
//print(array,size);
}
//display(&array[0]);
element* temp=&array[0];
//printf("Height of the tree is %d ",height(&array[0]));
while(temp->right!=NULL){
printf("Frequency : %d\n ",temp->frequency);
temp=temp->right;
}
}
int main(){
printf("Enter the string\n");
char string[100];
int freq[26],i,temp_count=0;
for(i=0;i<=25;i++) freq[i]=0;
scanf("%[^\n]",string);
for(i=0;i<strlen(string);i++) if(string[i]!=' ') freq[string[i]-'a']++;
for(i=0;i<=25;i++) if(freq[i]!=0) size++;//One can eliminate this loop if space is not a factor
element arr[size+1];
for(i=0;i<=25;i++){
if(freq[i]){
arr[temp_count].frequency=freq[i];
arr[temp_count].ch=(char)(i+'a');
arr[temp_count].left=arr[temp_count].right=NULL;
temp_count++;
}
}
for(i=size/2-1;i>=0;i--) heapify(arr,i);
HuffmanEncoding(arr);
return 0;
}