帮我用c语言写代码完成以下任务哈夫曼编码 任务：根据电文中各字符出现的频率，建立哈夫曼树，并设计字符的哈夫曼编码。 功能要求： 1) 建立并输出哈夫曼树的存储结构； 2) 根据哈夫曼树，设计并输出对应字符的哈夫曼编码； 3) 将指定接收到的电文进行译码并输出。 界面要求：程序运行后，给出菜单项的内容和输入提示： 1. 建立哈夫曼树 2. 哈夫曼编码 3. 译码 0. 退出 请选择0-3：

为了方便，我将分为三部分给你分别展示代码，包括建立哈夫曼树、哈夫曼编码和译码。

建立哈夫曼树：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_TREE_SIZE 100

typedef struct {
    char ch;            // 存储字符
    int weight;         // 存储权值
    int parent, lchild, rchild;   // 存储父节点和左右子节点的下标
} HTNode, *HuffmanTree;

void CreateHuffmanTree(HuffmanTree *HT, int n) {
    if (n <= 1) {
        return;
    }
    int m = 2 * n - 1;
    *HT = (HuffmanTree) malloc((m + 1) * sizeof(HTNode));
    for (int i = 1; i <= n; i++) {
        scanf(" %c %d", &(*HT)[i].ch, &(*HT)[i].weight);
        (*HT)[i].parent = 0;
        (*HT)[i].lchild = 0;
        (*HT)[i].rchild = 0;
    }
    for (int i = n + 1; i <= m; i++) {
        (*HT)[i].ch = ' ';
        (*HT)[i].weight = 0;
        (*HT)[i].parent = 0;
        (*HT)[i].lchild = 0;
        (*HT)[i].rchild = 0;
    }
    int s1, s2, min1 = 0, min2 = 0;
    for (int i = n + 1; i <= m; i++) {
        s1 = s2 = 0;
        min1 = min2 = 0;
        for (int j = 1; j < i; j++) {
            if ((*HT)[j].parent == 0) {
                if ((*HT)[j].weight < (*HT)[min1].weight) {
                    min2 = min1;
                    min1 = j;
                } else if ((*HT)[j].weight < (*HT)[min2].weight) {
                    min2 = j;
                }
            }
        }
        (*HT)[min1].parent = i;
        (*HT)[min2].parent = i;
        (*HT)[i].lchild = min1;
        (*HT)[i].rchild = min2;
        (*HT)[i].weight = (*HT)[min1].weight + (*HT)[min2].weight;
    }
}

void PrintHuffmanTree(HuffmanTree HT, int n) {
    printf("Huffman Tree:\n");
    for (int i = 1; i <= 2 * n - 1; i++) {
        printf("%d: %c %d %d %d %d\n", i, HT[i].ch, HT[i].weight, HT[i].parent, HT[i].lchild, HT[i].rchild);
    }
}

哈夫曼编码：

#define MAX_CODE_LEN 20

typedef struct {
    char ch;
    char code[MAX_CODE_LEN];
} HCode;

void HuffmanCoding(HuffmanTree HT, int n, HCode *HC) {
    char *cd = (char *) malloc(n * sizeof(char));
    cd[n - 1] = '\0';
    for (int i = 1; i <= n; i++) {
        int start = n - 1;
        int c = i;
        int f = HT[i].parent;
        while (f != 0) {
            if (HT[f].lchild == c) {
                cd[--start] = '0';
            } else {
                cd[--start] = '1';
            }
            c = f;
            f = HT[f].parent;
        }
        strcpy(HC[i].code, &cd[start]);
        HC[i].ch = HT[i].ch;
    }
    free(cd);
}

void PrintHuffmanCode(HCode *HC, int n) {
    printf("Huffman Code:\n");
    for (int i = 1; i <= n; i++) {
        printf("%c: %s\n", HC[i].ch, HC[i].code);
    }
}

译码：

void Decode(HuffmanTree HT, int n) {
    printf("Please input the coded message:\n");
    char code[100];
    scanf("%s", code);
    int p = 2 * n - 1;
    for (int i = 0; code[i] != '\0'; i++) {
        if (code[i] == '0') {
            p = HT[p].lchild;
        } else {
            p = HT[p].rchild;
        }
        if (HT[p].lchild == 0 && HT[p].rchild == 0) {
            printf("%c", HT[p].ch);
            p = 2 * n - 1;
        }
    }
    printf("\n");
}

完整代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_TREE_SIZE 100
#define MAX_CODE_LEN 20

typedef struct {
    char ch;            // 存储字符
    int weight;         // 存储权值
    int parent, lchild, rchild;   // 存储父节点和左右子节点的下标
} HTNode, *HuffmanTree;

typedef struct {
    char ch;
    char code[MAX_CODE_LEN];
} HCode;

void CreateHuffmanTree(HuffmanTree *HT, int n) {
    if (n <= 1) {
        return;
    }
    int m = 2 * n - 1;
    *HT = (HuffmanTree) malloc((m + 1) * sizeof(HTNode));
    for (int i = 1; i <= n; i++) {
        scanf(" %c %d", &(*HT)[i].ch, &(*HT)[i].weight);
        (*HT)[i].parent = 0;
        (*HT)[i].lchild = 0;
        (*HT)[i].rchild = 0;
    }
    for (int i = n + 1; i <= m; i++) {
        (*HT)[i].ch = ' ';
        (*HT)[i].weight = 0;
        (*HT)[i].parent = 0;
        (*HT)[i].lchild = 0;
        (*HT)[i].rchild = 0;
    }
    int s1, s2, min1 = 0, min2 = 0;
    for (int i = n + 1; i <= m; i++) {
        s1 = s2 = 0;
        min1 = min2 = 0;
        for (int j = 1; j < i; j++) {
            if ((*HT)[j].parent == 0) {
                if ((*HT)[j].weight < (*HT)[min1].weight) {
                    min2 = min1;
                    min1 = j;
                } else if ((*HT)[j].weight < (*HT)[min2].weight) {
                    min2 = j;
                }
            }
        }
        (*HT)[min1].parent = i;
        (*HT)[min2].parent = i;
        (*HT)[i].lchild = min1;
        (*HT)[i].rchild = min2;
        (*HT)[i].weight = (*HT)[min1].weight + (*HT)[min2].weight;
    }
}

void PrintHuffmanTree(HuffmanTree HT, int n) {
    printf("Huffman Tree:\n");
    for (int i = 1; i <= 2 * n - 1; i++) {
        printf("%d: %c %d %d %d %d\n", i, HT[i].ch, HT[i].weight, HT[i].parent, HT[i].lchild, HT[i].rchild);
    }
}

void HuffmanCoding(HuffmanTree HT, int n, HCode *HC) {
    char *cd = (char *) malloc(n * sizeof(char));
    cd[n - 1] = '\0';
    for (int i = 1; i <= n; i++) {
        int start = n - 1;
        int c = i;
        int f = HT[i].parent;
        while (f != 0) {
            if (HT[f].lchild == c) {
                cd[--start] = '0';
            } else {
                cd[--start] = '1';
            }
            c = f;
            f = HT[f].parent;
        }
        strcpy(HC[i].code, &cd[start]);
        HC[i].ch = HT[i].ch;
    }
    free(cd);
}

void PrintHuffmanCode(HCode *HC, int n) {
    printf("Huffman Code:\n");
    for (int i = 1; i <= n; i++) {
        printf("%c: %s\n", HC[i].ch, HC[i].code);
    }
}

void Decode(HuffmanTree HT, int n) {
    printf("Please input the coded message:\n");
    char code[100];
    scanf("%s", code);
    int p = 2 * n - 1;
    for (int i = 0; code[i] != '\0'; i++) {
        if (code[i] == '0') {
            p = HT[p].lchild;
        } else {
            p = HT[p].rchild;
        }
        if (HT[p].lchild == 0 && HT[p].rchild == 0) {
            printf("%c", HT[p].ch);
            p = 2 * n - 1;
        }
    }
    printf("\n");
}

int main() {
    HuffmanTree HT = NULL;
    HCode HC[MAX_TREE_SIZE];
    int n = 0;
    while (1) {
        printf("1. Create Huffman Tree\n");
        printf("2. Huffman Coding\n");
        printf("3. Decode\n");
        printf("0. Exit\n");
        printf("Please select 0-3: ");
        int choice;
        scanf("%d", &choice);
        switch (choice) {
            case 0:
                return 0;
            case 1:
                printf("Please input the number of characters: ");
                scanf("%d", &n);
                CreateHuffmanTree(&HT, n);
                PrintHuffmanTree(HT, n);
                break;
            case 2:
                HuffmanCoding(HT, n, HC);
                PrintHuffmanCode(HC, n);
                break;
            case 3:
                Decode(HT, n);
                break;
            default:
                printf("Invalid input\n");
                break;
        }
    }
}