哈夫曼编译码器

//eg:
//    4        A B C D        9 5 2 4
//    A: 0    B: 10    C: 110    D: 111
//  ABCDCBA    010110111110100
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<conio.h>
#define OK 1
#define ERROR 0
typedef struct HTNode{
    char ch;
    int weight;
    int parent, lchild, rchild;
} HTNode;
typedef struct HTNode* HuffmanTree;
typedef char** HuffmanCode;
//定义全局变量
HuffmanTree HT;
HuffmanCode HC;
int n;
//选择两个最小结点
void select(int k, int *s1, int *s2){
    int i, ti, t=1000;
    for(i = 1; i <= k; i++){
        if(!HT[i].parent){ 
            if(t > HT[i].weight){
                t = HT[i].weight;//t最后为最小的weight
                ti = i;
            }
        }
    }
    *s1 = ti;
    t = 1000;
    ti = 0;
    for(i = 1; i <= k; i++){
        if((!HT[i].parent) && i!=*s1){ //parent为0
            if(t > HT[i].weight){
                t = HT[i].weight;
                ti = i;
            }
        }
    }
    *s2 = ti;
}
//打印哈夫曼树
void printHT(int m){
    int i;
    printf("\n");
    printf("char  weight  parent  lchild  rchild\n");
    for(i = 1; i <= m; i++){
        printf("  %c  %5d  %5d  %5d  %5d\n", HT[i].ch, HT[i].weight, HT[i].parent, HT[i].lchild, HT[i].rchild);
    }
    printf("\n");
}
//初始化(建树和编码表)
int Init(){
    int m = 2*n-1;
    int i, s1, s2;
    int w[n+1];//weight 0下标不使用
    char ch[n+1];//字符 
    char title;
    char* cd;
    int start, c, f;
    //建立哈夫曼树
    while(title = getchar() != '\n');
    printf("■请输入各字符(用空格分开):");
    for(i=1; i<=n; i++){
        scanf("%c", &ch[i]);
        getchar();
    }
    printf("■请输入各权值(用空格分开):");
    for(i=1; i<=n; i++)
        scanf("%d", &w[i]);
    HT = (HuffmanTree)malloc((m+1)*sizeof(HTNode));//0号节点不使用
    for(i=1; i<=n; i++){
        HT[i].ch = ch[i];
        HT[i].weight = w[i];
        HT[i].lchild = 0;
        HT[i].rchild = 0;
        HT[i].parent = 0;
    }
    for(; i<=m; i++){
        HT[i].ch='-';
        HT[i].weight=0;
        HT[i].lchild=0;
        HT[i].rchild=0;
        HT[i].parent=0;
    }
    for(i=n+1; i<=m; i++){
        select(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;
    }
    printf("\n■生成的哈夫曼树为:");
    printHT(m);
    //从叶子到根逆向求每个字符的哈夫曼编码 
    HC = (HuffmanCode)malloc((n+1)*sizeof(char*));//分配n个字符编码的头指针向量 
    cd = (char*)malloc(n*sizeof(char));//分配求编码的工作空间 
    cd[n-1]='\0';//编码结束符 
    printf("■其编码表为:\n");
    for(i=1; i<=n; i++){//逐个字符求哈夫曼编码 
        start = n-1;//编码结束符位置 
        for(c = i, f = HT[i].parent; f != 0; c = f, f = HT[f].parent){
            if(HT[f].lchild==c)
                cd[--start]='0';
            else
                cd[--start]='1';
        }
        HC[i] = (char*)malloc((n-start)*sizeof(char));//为第i个字符编码分配空间 
        strcpy(HC[i], &cd[start]);//从cd复制编码到HC 
        printf("%c: ", HT[i].ch);
        puts(HC[i]);
    }
    free(cd);
    return OK;
}
//编码
int Encoding(){
    char s[20], title;
    int i, j;
    while(title = getchar() != '\n');
    printf("\n■请输入字符串:\n");
    scanf("%s", s);
    printf("■编码结果为:\n");
    for(i=0; s[i]!='\0'; i++){
        for(j=1; j<=n; j++){
            if(s[i]==HT[j].ch){
                printf("%s", HC[j]);
                continue;
            }
        }
    }
    printf("\n");
    return OK;
}
//译码
int Decoding(){
    char s[20], title;
    int i=0, p=2*n-1;//p在根节点位置;
    while(title = getchar() != '\n');
    printf("\n■请输入编码:\n");
    scanf("%s", s);
    printf("■译码结果为:\n");
    for(i = 0; s[i] != '\0'; i++){
        if(s[i]=='0')
            p=HT[p].lchild;
        if(s[i]=='1')
            p=HT[p].rchild;
        if(p<=n){
            printf("%c", HT[p].ch);
            p=2*n-1;
        }
    }
    printf("\n");
    return OK;
}
//菜单
void menu(){
        printf("■■■■■哈夫曼编译码器■■■■■\n");
        printf("■\t ★1-建立哈夫曼树\t■\n");
        printf("■\t ★2-编码\t\t■\n");
        printf("■\t ★3-译码\t\t■\n");
        printf("■\t ★4-退出\t\t■\n");
        printf("■■■■■■■■■■■■■■■■■\n");
        printf("■请选择:");
}
int main(){
    char ch, title;
    while(1){
        menu();
        scanf("%c", &ch);
        switch(ch){
        case '1':
            printf("\n■请输入字符数n(n>0):");
            scanf("%d", &n);
            Init();
            break;
        case '2':
            Encoding();
            break;
        case '3':
            Decoding();
            break;
        case '4':
            printf("Finished, God bless you!"); 
            exit(0);
        }
        printf("\n");
        while(title = getchar() != '\n');
    }
    return 0;
}