#include<iostream>
#include<string>
using namespace std;
struct Node
{
  double weight;
  string ch;
  string code;
  int lchild, rchild, parent;
};
void Select(Node huffTree[], int *a, int *b, int n)//找權(quán)值最小的兩個a和b
{
  int i;
  double weight = 0; //找最小的數(shù)
  for (i = 0; i <n; i++)
  {
    if (huffTree[i].parent != -1)   //判斷節(jié)點(diǎn)是否已經(jīng)選過
      continue;
    else
    {
      if (weight == 0)
      {
        weight = huffTree[i].weight;
        *a = i;
      }
      else
      {
        if (huffTree[i].weight < weight)
        {
          weight = huffTree[i].weight;
          *a = i;
        }
      }
    }
  }
  weight = 0; //找第二小的數(shù)
  for (i = 0; i < n; i++)
  {
    if (huffTree[i].parent != -1 || (i == *a))//排除已選過的數(shù)
      continue;
    else
    {
      if (weight == 0)
      {
        weight = huffTree[i].weight;
        *b = i;
      }
      else
      {
        if (huffTree[i].weight < weight)
        {
          weight = huffTree[i].weight;
          *b = i;
        }
      }
    }
  }
  int temp;
  if (huffTree[*a].lchild < huffTree[*b].lchild) //小的數(shù)放左邊
  {
    temp = *a;
    *a = *b;
    *b = temp;
  }
}
void Huff_Tree(Node huffTree[], int w[], string ch[], int n)
{
  for (int i = 0; i < 2 * n - 1; i++) //初始過程
  {
    huffTree[i].parent = -1;
    huffTree[i].lchild = -1;
    huffTree[i].rchild = -1;
    huffTree[i].code = "";
  }
  for (int i = 0; i < n; i++)
  {
    huffTree[i].weight = w[i];
    huffTree[i].ch = ch[i];
  }
  for (int k = n; k < 2 * n - 1; k++)
  {
    int i1 = 0;
    int i2 = 0;
    Select(huffTree, &i1, &i2, k); //將i1，i2節(jié)點(diǎn)合成節(jié)點(diǎn)k
    huffTree[i1].parent = k;
    huffTree[i2].parent = k;
    huffTree[k].weight = huffTree[i1].weight + huffTree[i2].weight;
    huffTree[k].lchild = i1;
    huffTree[k].rchild = i2;
  }
}
void Huff_Code(Node huffTree[], int n)
{
  int i, j, k;
  string s = "";
  for (i = 0; i < n; i++)
  {
    s = "";
    j = i;
    while (huffTree[j].parent != -1) //從葉子往上找到根節(jié)點(diǎn)
    {
      k = huffTree[j].parent;
      if (j == huffTree[k].lchild) //如果是根的左孩子，則記為0
      {
        s = s + "0";
      }
      else
      {
        s = s + "1";
      }
      j = huffTree[j].parent;
    }
    cout << "字符 " << huffTree[i].ch << " 的編碼：";
    for (int l = s.size() - 1; l >= 0; l--)
    {
      cout << s[l];
      huffTree[i].code += s[l]; //保存編碼
    }
    cout << endl;
  }
}
string Huff_Decode(Node huffTree[], int n,string s)
{
  cout << "解碼后為：";
  string temp = "",str="";//保存解碼后的字符串
  for (int i = 0; i < s.size(); i++)
  {
    temp = temp + s[i];
    for (int j = 0; j < n; j++)
    {
      if (temp == huffTree[j].code)
      {
        str=str+ huffTree[j].ch;
        temp = "";
        break;
      }
      else if (i == s.size()-1&&j==n-1&&temp!="")//全部遍歷后沒有
      {
        str= "解碼錯誤！";
      }
    }
  }
  return str;
}
int main()
{
  //編碼過程
  const int n=5;
  Node huffTree[2 * n];
  string str[] = { "A", "B", "C", "D", "E"};
  int w[] = { 30, 30, 5, 20, 15 };
  Huff_Tree(huffTree, w, str, n);
  Huff_Code(huffTree, n);
  //解碼過程
  string s;
  cout << "輸入編碼：";
  cin >> s;
  cout << Huff_Decode(huffTree, n, s)<< endl;;
  system("pause");
  return 0;
}