哈夫曼樹編碼並解碼（加強版）

本代碼流程：

隨機輸入一段字符串--->根據輸入字符串得到每個字符權重（頻數）並輸出--->得到每個字符對應哈夫曼編碼並輸出--->輸入一段哈夫曼編碼--->利用每個字符對應的哈夫曼編碼來解碼

技術支持：

1.如何得到每個自負權重，上上個博客，網址如下：

https://www.cnblogs.com/2019-12-10-18ykx/p/12898245.html

2.如何判斷兩字符串是否相等，上個博客，網址如下：

https://www.cnblogs.com/2019-12-10-18ykx/p/12902210.html

這里是代碼：

main.cpp

#include <iostream>
#include "哈夫曼樹.h"
#include <map>
#include <set>
#include <string>
using namespace std;
int main() {
    HuffmanTree HT;
    HuffmanCode HC;
    int *wei, n = 0, i;
    char *ch;
    string s;
    cout << "請輸入一段字符串(字符串長度不要超過100):";
    cin >> s;
    map<char, int> m;
    int j = 1;
    for (auto & i : s)
    {
        m[i]++;
    }
        for (auto & i : m)
    {
        cout << i.first << ' ' << i.second << endl;
        n++;
    }
    wei = (int *)malloc((n + 1) * sizeof(int));
    ch = (char*)malloc((n + 1) * sizeof(char));
    for (auto & i : m)
    {
        ch[j] = i.first;
        wei[j] = i.second;
        j++;
    }
    createHuffmanTree(&HT, n, wei, ch);
    createHuffmanCode(&HT, &HC, n);
    return 0;
}

哈夫曼樹.h（其實Decode解碼函數可以用void類型的，但是我懶得改了）

#include <iostream>
using namespace std;
typedef struct {
    int weight;
    int lchild, rchild, parent;
    char c;
}Node, *HuffmanTree;
typedef char *HuffmanCode;
void select(HuffmanTree *huffmantree, int n, int *s1, int *s2);
void createHuffmanTree(HuffmanTree *huffmantree, int n, int w[], char cha[]);
void createHuffmanCode(HuffmanTree *huffmantree, HuffmanCode *huffmancode, int n);
string Decode(HuffmanTree *huffmantree, HuffmanCode *huffmancode, int n, string s);

哈夫曼樹.cpp

#include <iostream>
#include "哈夫曼樹.h"
#include <string>
using namespace std;
//找權值最小的結點
void select(HuffmanTree *huffmantree,int n,int *s1,int *s2) {
    int i;//作為計數器
    int min1, min2, m1=0, m2;//權值最小和權值次小,權值最小和次小所在位置
    min1 = 999;
    min2 = 999;
    for (i = 1; i <= n; i++) {
        if ((*huffmantree)[i].parent == 0) {//保證父節點不為0
            if (min1 > (*huffmantree)[i].weight) {
                min2 = min1;
                m2 = m1;
                min1 = (*huffmantree)[i].weight;
                m1 = i;
            }
            else if (min2 > (*huffmantree)[i].weight) {
                min2 = (*huffmantree)[i].weight;
                m2 = i;
            }
        }
    }
    *s1 = m1;
    *s2 = m2;
}
//初始化節點，構造哈夫曼樹
void createHuffmanTree(HuffmanTree *huffmantree,int n,int w[],char cha[]) {
    int i;
    int m = 2 * n - 1;
    *huffmantree = (HuffmanTree)malloc((m + 1) * sizeof(Node));
    //葉子節點的初始化
    for (i = 1; i <= n; i++) {
        (*huffmantree)[i].parent = 0;
        (*huffmantree)[i].lchild = 0;
        (*huffmantree)[i].rchild = 0;
        (*huffmantree)[i].c = cha[i];
        (*huffmantree)[i].weight = w[i];
    }
    //非葉子節點的初始化
    for (i = n + 1; i <= m; i++) {
        (*huffmantree)[i].parent = 0;
        (*huffmantree)[i].lchild = 0;
        (*huffmantree)[i].rchild = 0;
        (*huffmantree)[i].weight = 0;
    }
    //開始構建哈夫曼樹
    cout << "哈夫曼樹：" << endl;
    cout << "父節點權值     (左孩子權值    右孩子權值)" << endl;
    int s1, s2;//這是兩個權值最小的結點所在位置
    for (i = n + 1; i <= m; i++) {
        //尋找parent為0，且權值最小的兩個結點
        select(huffmantree, i-1, &s1, &s2);
        (*huffmantree)[s1].parent = i;
        (*huffmantree)[s2].parent = i;
        (*huffmantree)[i].lchild = s1;
        (*huffmantree)[i].rchild = s2;
        (*huffmantree)[i].weight = (*huffmantree)[s1].weight + (*huffmantree)[s2].weight;
        cout << "    " << (*huffmantree)[i].weight << "          " << (*huffmantree)[s1].weight << "          " << (*huffmantree)[s2].weight << endl;
    }
}
//初始化哈夫曼編碼？！生成哈夫曼編碼
void createHuffmanCode(HuffmanTree *huffmantree,HuffmanCode *huffmancode,int n) {
    int i, start, f;
    char *cd;
    int c;
    huffmancode = (HuffmanCode*)malloc((n + 1) * sizeof(char*));//n個頭指針向量
    cd = (char*)malloc(n * sizeof(char));
    cd[n - 1] = '\0';//編碼結束符
    for (i = 1; i <= n; ++i) {
        start = n - 1;
        for (c = i, f = (*huffmantree)[i].parent; f != 0; c = f, f = (*huffmantree)[f].parent) {
            if ((*huffmantree)[f].lchild == c) cd[--start] = '0';
            else cd[--start] = '1';
        }
        //為第i個字符編碼分配空間
        huffmancode[i] = (char*)malloc((n - start) * sizeof(char));
        strcpy(huffmancode[i], &cd[start]);
    }
    free(cd);
    //開始打印編碼
    cout << "哈夫曼字符       權值       對應編碼" << endl;
    for (i = 1; i <= n; i++) {
        cout << "     " << (*huffmantree)[i].c << "       " << (*huffmantree)[i].weight << "        " << huffmancode[i] << endl;
    }
    //在這里解碼，一定要成功！！！
    string s;
    cout << "請輸入待解碼的哈夫曼編碼：";
    cin >> s;
    Decode(huffmantree, huffmancode, n, s);
}

string Decode(HuffmanTree *huffmantree,HuffmanCode *huffmancode,int n,string s) {
    char *c;
    int i, j, k = 0;
    for (i = 1; i <= n; i++) {
        cout << (*huffmantree)[i].c;
        cout << huffmancode[i] << endl;
    }
    c = (char*)malloc(s.size() * sizeof(char));//c的內存空間
    for (i = 0; i < s.size(); i++) {
        c[k] = s[i];
        c[k + 1] = '\0';
        for (j = 1; j <= n; j++) {
            if (strcmp(c,huffmancode[j])==0) {//找到哈夫曼編碼
                cout << (*huffmantree)[j].c;
                k = -1;
                c[0] = '\0';
                break;
            }
            else if ((i == s.size() - 1) && j == n && c[0] != '\0') cout << "ERROR!!!" << endl;
        }
        k++;
    }
    return 0;
}

調試結果如下：

真的真的是經歷了九九八十一難才完成！！！