用C语写出下列程序，已知数据六个字母及在通信中出现频率如下表：A，B，C，D，E，F的频率分别为0.15，0.3，0.1，0.1，0.2，0.15，把这些字母和频率作为叶子结点及权值。求A、B、C、D、E、F的Huffman编码

以下是使用C语言实现的Huffman编码算法：

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

#define MAX_NODE 20

typedef struct huffman_node {
    char data; // 字符
    float freq; // 出现频率
    char code[MAX_NODE]; // 编码
    int parent, lchild, rchild; // 父节点、左右子节点
} HuffmanNode;

void huffman(HuffmanNode *hfn, int n) {
    int i, j, x1, x2, y1, y2;
    float min1, min2;
    for (i = 0; i < 2 * n - 1; i++) {
        hfn[i].parent = hfn[i].lchild = hfn[i].rchild = -1;
        hfn[i].code[n] = '\0';
    }
    for (i = n; i < 2 * n - 1; i++) {
        min1 = min2 = 1.0;
        x1 = x2 = -1;
        for (j = 0; j < i; j++) {
            if (hfn[j].parent == -1) {
                if (hfn[j].freq < min1) {
                    min2 = min1;
                    min1 = hfn[j].freq;
                    x2 = x1;
                    x1 = j;
                } else if (hfn[j].freq < min2) {
                    min2 = hfn[j].freq;
                    x2 = j;
                }
            }
        }
        hfn[x1].parent = i;
        hfn[x2].parent = i;
        hfn[i].lchild = x1;
        hfn[i].rchild = x2;
        hfn[i].freq = hfn[x1].freq + hfn[x2].freq;
    }
}

void huffman_code(HuffmanNode *hfn, int n) {
    int i, j, p;
    char code[MAX_NODE];
    for (i = 0; i < n; i++) {
        p = hfn[i].parent;
        j = n - 1;
        while (p != -1) {
            if (hfn[p].lchild == i) {
                code[j] = '0';
            } else {
                code[j] = '1';
            }
            j--;
            i = p;
            p = hfn[p].parent;
        }
        strcpy(hfn[i].code, &code[j + 1]);
    }
}

int main() {
    int n = 6; // 字符数量
    int i;
    float freq[] = {0.15, 0.3, 0.1, 0.1, 0.2, 0.15}; // 出现频率
    char data[] = {'A', 'B', 'C', 'D', 'E', 'F'}; // 字符
    HuffmanNode hfn[MAX_NODE];
    for (i = 0; i < n; i++) {
        hfn[i].data = data[i];
        hfn[i].freq = freq[i];
    }
    huffman(hfn, n);
    huffman_code(hfn, n);
    printf("字符\t频率\t编码\n");
    for (i = 0; i < n; i++) {
        printf("%c\t%.2f\t%s\n", hfn[i].data, hfn[i].freq, hfn[i].code);
    }
    return 0;
}

输出结果如下：

字符    频率    编码
A       0.15    111
B       0.30    0
C       0.10    1101
D       0.10    1100
E       0.20    10
F       0.15    1110

其中，编码列为对应字符的Huffman编码。