C++实现Huffman的编解码

typedef struct Tree
{
 int freq;//频率
 int key;//键值
 struct Tree *left, *right;
 Tree(int fr=0, int k=0,Tree *l=nullptr, Tree *r=nullptr):
  freq(fr),key(k),left(l),right(r){};
}Tree,*pTree;

void read(){
 int a;
 
 std::ios::sync_with_stdio(false);
 while(cin>>a){
  if(freq.find(a)==freq.end()) {freq[a]=1;}
  else {freq[a]++;}
 }
 
}

void huffman()
{
 int i;
 string c;
 int fr;
 auto it = freq.begin();
 while(it!=freq.end()){
  Tree *pt= new Tree;
  pt->key = it->first;
  pt->freq = it->second;
  it++;
  th.Insert(pt);//此处的th为一种优先队列
 }
 
 while(true)//构建哈夫曼树
 {
 
  Tree *proot = new Tree;
  pTree pl,pr;
  pl = th.findMin();
  th.Delete(0);
  if(th.isEmpty()){
    th.Insert(pl);
    break;
  }
 
  pr = th.findMin();
  th.Delete(0);
  //合并节点
  proot->freq = pl->freq + pr->freq;
  std::ios::sync_with_stdio(false);
  proot->left = pl;
  proot->right = pr;
  th.Insert(proot);
  //合并后再插入
 }
 
 string s;
 
 print_Code(th.findMin(), s);
 
 del(th.findMin());
}

void print_Code(Tree *proot, string st)//从根节点开始打印，左0右1
{
 if(proot == NULL)
  return ;
 if(proot->left)
 {
  st +='0';
 }
 print_Code(proot->left, st);
 std::ios::sync_with_stdio(false);
 if(!proot->left && !proot->right)
 {
  cout<<proot->key<<" ";
  for(size_t i=0; i<st.length(); ++i){
   cout<<st[i];ml+=st[i];
  }
  cout<<endl;encoded[proot->key]=ml;ml="";
 }
 st.pop_back();
 if(proot->right)
  st+='1';
 print_Code(proot->right, st);
}
 
 
void del(Tree *proot)
{
 if(proot == nullptr)
  return ;
 del(proot->left);
 del(proot->right);
 delete proot;
}

while(in>>a){
   int x=atoi(a.c_str());
   auto m=encoded.find(x);
   //encoded是另外一个哈希表用于记录元素及它的编码
   if(m==encoded.end()) continue;
   else {
     string t=m->second;
     ss+=t;
   }
   
 }
 unsigned char buf = 0;
 int count = 0;
 int i = 0;
 while(ss[i] != '\0')//位写入，8个为一组
 {
  buf = buf | ((ss[i++]-'0') << (7 - count));
  count++;
  if (count == 8)
  {
   count = 0;
   fout << buf;
   buf = 0;
  }
 }
 if(count != 0)
  fout << buf;

void decode(){
 auto it=decoded.begin();
 Tree *p=proot;
 while(it!=decoded.end()){
   string s=it->first;int t=it->second;int i=0;
   while(i<s.length()){
    if(s[i]=='0') {
     if(proot->left==nullptr) proot->left=new Tree(5);
     proot=proot->left;
     }
    else{
     if(proot->right==nullptr) proot->right=new Tree(5);
     proot=proot->right;
     }
    i++;
   }
   proot->data=t;
   proot=p;
   it++;
 }
 
}

while (f.get(c)){
   stringstream a;
   for (int i = 7; i > 0; i--)
    a<<((c >> i) & 1);
   a<<(c&1);
   m+=a.str();//将位转为字符串
 }

int i=0;Tree *p=proot;
 
 while(i<m.length()){
   if(m[i]=='0'&&proot->left!=nullptr)
    {proot=proot->left;i++;}
   else if(m[i]=='1'&&proot->right!=nullptr)
    {proot=proot->right;i++;}
   else
    {cout<<proot->data<<endl;proot=p;}
 }