# Construct Huffman tree and find Huffman code (reverse from leaf to root)

Time：2022-1-4
``````#include<iostream>
#include<string.h>
using namespace std;
typedef struct{
int weight;
int parent,lchild,rchild;
}HTNode,*HuffmanTree;
void Select(HuffmanTree HT,int len,int &s1,int &s2){
int i,min1=0x3f3f3f3f,min2=0x3f3f3f3f;
for(i=1;i<=len;i++){
if(HT[i].weight<min1&&HT[i].parent==0){
min1=HT[i].weight;
s1=i;
}
}
int temp=HT[s1].weight;
HT[s1].weight=0x3f3f3f3f;
for(i=1;i<=len;i++){
if(HT[i].weight<min2&&HT[i].parent==0){
min2=HT[i].weight;
s2=i;
}
}
HT[s1].weight=temp;
}
//Constructing Huffman tree
void CreatHuffmanTree(HuffmanTree &HT,int n){
int m,s1,s2,i;
if(n<=1) return;
m=2*n-1;
HT=new HTNode[m+1];
for(i=1;i<=m;++i){
HT[i].parent=0;
HT[i].lchild=0;
HT[i].rchild=0;
}
Cout < < "leaf node weight:";
for(i=1;i<=n;++i)
cin>>HT[i].weight;
for(i=n+1;i<=m;++i){
Select(HT,i-1,s1,s2);
HT[s1].parent=i;
HT[s2].parent=i;
HT[i].lchild=s1;
HT[i].rchild=s2 ;
HT[i].weight=HT[s1].weight+HT[s2].weight;
}
}
typedef char **HuffmanCode;
//Huffman coding
void CreatHuffmanCode(HuffmanTree HT,HuffmanCode &HC,int n){
int i,start,c,f;
HC=new char*[n+1];
char *cd=new char[n];
cd[n-1]='#include<iostream>
#include<string.h>
using namespace std;
typedef struct{
int weight;
int parent,lchild,rchild;
}HTNode,*HuffmanTree;
void Select(HuffmanTree HT,int len,int &s1,int &s2){
int i,min1=0x3f3f3f3f,min2=0x3f3f3f3f;
for(i=1;i<=len;i++){
if(HT[i].weight<min1&&HT[i].parent==0){
min1=HT[i].weight;
s1=i;
}
}
int temp=HT[s1].weight;
HT[s1].weight=0x3f3f3f3f;
for(i=1;i<=len;i++){
if(HT[i].weight<min2&&HT[i].parent==0){
min2=HT[i].weight;
s2=i;
}
}
HT[s1].weight=temp;
}
//Constructing Huffman tree
void CreatHuffmanTree(HuffmanTree &HT,int n){
int m,s1,s2,i;
if(n<=1) return;
m=2*n-1;
HT=new HTNode[m+1];
for(i=1;i<=m;++i){
HT[i].parent=0;
HT[i].lchild=0;
HT[i].rchild=0;
}
Cout < < "leaf node weight:";
for(i=1;i<=n;++i)
cin>>HT[i].weight;
for(i=n+1;i<=m;++i){
Select(HT,i-1,s1,s2);
HT[s1].parent=i;
HT[s2].parent=i;
HT[i].lchild=s1;
HT[i].rchild=s2 ;
HT[i].weight=HT[s1].weight+HT[s2].weight;
}
}
typedef char **HuffmanCode;
//Huffman coding
void CreatHuffmanCode(HuffmanTree HT,HuffmanCode &HC,int n){
int i,start,c,f;
HC=new char*[n+1];
char *cd=new char[n];
cd[n-1]='\0';
for(i=1;i<=n;++i){
start=n-1;
c=i;
f=HT[i].parent;
while(f!=0){
--start;
if(HT[f].lchild==c)
cd[start]='0';
else
cd[start]='1';
c=f;
f=HT[f].parent;
}
HC[i]=new char[n-start];
strcpy(HC[i], &cd[start]);
}
delete cd;
}
void show(HuffmanTree HT,HuffmanCode HC,int n){
for(int i=1;i<=n;i++)
cout<<HT[i]. Weight < < Huffman code is: < < HC [i] < < endl;
}
int main(){
HuffmanTree HT;
int n;
Cout < < "number of leaf nodes:";
cin>>n;
CreatHuffmanTree(HT,n);
HuffmanCode HC;
CreatHuffmanCode(HT,HC,n);
show(HT,HC,n);
}';
for(i=1;i<=n;++i){
start=n-1;
c=i;
f=HT[i].parent;
while(f!=0){
--start;
if(HT[f].lchild==c)
cd[start]='0';
else
cd[start]='1';
c=f;
f=HT[f].parent;
}
HC[i]=new char[n-start];
strcpy(HC[i], &cd[start]);
}
delete cd;
}
void show(HuffmanTree HT,HuffmanCode HC,int n){
for(int i=1;i<=n;i++)
cout<<HT[i]. Weight < < Huffman code is: < < HC [i] < < endl;
}
int main(){
HuffmanTree HT;
int n;
Cout < < "number of leaf nodes:";
cin>>n;
CreatHuffmanTree(HT,n);
HuffmanCode HC;
CreatHuffmanCode(HT,HC,n);
show(HT,HC,n);
}``````

## Strong, copy difference

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