根据某字符文件统计字符出现频度，构造Huffman 树，编制Huffman 编码，并将给定字符文件编码，生成编码文件；再将给定编码文件解码，生成字符文件。（要求按二进制位表示编码）c语言编码并画出流程图

以下是C语言实现Huffman编码的代码，同时也包括了生成编码文件和解码的功能：

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

#define MAX_TREE_HT 100

struct MinHeapNode {
    char data;
    unsigned freq;
    struct MinHeapNode *left, *right;
};

struct MinHeap {
    unsigned size;
    unsigned capacity;
    struct MinHeapNode **array;
};

struct MinHeapNode *newNode(char data, unsigned freq) {
    struct MinHeapNode *temp = (struct MinHeapNode *)malloc(sizeof(struct MinHeapNode));
    temp->left = temp->right = NULL;
    temp->data = data;
    temp->freq = freq;
    return temp;
}

struct MinHeap *createMinHeap(unsigned capacity) {
    struct MinHeap *minHeap = (struct MinHeap *)malloc(sizeof(struct MinHeap));
    minHeap->size = 0;
    minHeap->capacity = capacity;
    minHeap->array = (struct MinHeapNode **)malloc(minHeap->capacity * sizeof(struct MinHeapNode *));
    return minHeap;
}

void swapMinHeapNode(struct MinHeapNode **a, struct MinHeapNode **b) {
    struct MinHeapNode *t = *a;
    *a = *b;
    *b = t;
}

void minHeapify(struct MinHeap *minHeap, int idx) {
    int smallest = idx;
    int left = 2 * idx + 1;
    int right = 2 * idx + 2;
    if (left < minHeap->size && minHeap->array[left]->freq < minHeap->array[smallest]->freq) {
        smallest = left;
    }
    if (right < minHeap->size && minHeap->array[right]->freq < minHeap->array[smallest]->freq) {
        smallest = right;
    }
    if (smallest != idx) {
        swapMinHeapNode(&minHeap->array[smallest], &minHeap->array[idx]);
        minHeapify(minHeap, smallest);
    }
}

int isSizeOne(struct MinHeap *minHeap) {
    return (minHeap->size == 1);
}

struct MinHeapNode *extractMin(struct MinHeap *minHeap) {
    struct MinHeapNode *temp = minHeap->array[0];
    minHeap->array[0] = minHeap->array[minHeap->size - 1];
    --minHeap->size;
    minHeapify(minHeap, 0);
    return temp;
}

void insertMinHeap(struct MinHeap *minHeap, struct MinHeapNode *minHeapNode) {
    ++minHeap->size;
    int i = minHeap->size - 1;
    while (i && minHeapNode->freq < minHeap->array[(i - 1) / 2]->freq) {
        minHeap->array[i] = minHeap->array[(i - 1) / 2];
        i = (i - 1) / 2;
    }
    minHeap->array[i] = minHeapNode;
}

void buildMinHeap(struct MinHeap *minHeap) {
    int n = minHeap->size - 1;
    int i;
    for (i = (n - 1) / 2; i >= 0; --i) {
        minHeapify(minHeap, i);
    }
}

void printArr(int arr[], int n) {
    int i;
    for (i = 0; i < n; ++i) {
        printf("%d", arr[i]);
    }
    printf("\n");
}

int isLeaf(struct MinHeapNode *root) {
    return !(root->left) && !(root->right);
}

struct MinHeap *createAndBuildMinHeap(char data[], int freq[], int size) {
    struct MinHeap *minHeap = createMinHeap(size);
    for (int i = 0; i < size; ++i) {
        minHeap->array[i] = newNode(data[i], freq[i]);
    }
    minHeap->size = size;
    buildMinHeap(minHeap);
    return minHeap;
}

struct MinHeapNode *buildHuffmanTree(char data[], int freq[], int size) {
    struct MinHeapNode *left, *right, *top;
    struct MinHeap *minHeap = createAndBuildMinHeap(data, freq, size);
    while (!isSizeOne(minHeap)) {
        left = extractMin(minHeap);
        right = extractMin(minHeap);
        top = newNode('$', left->freq + right->freq);
        top->left = left;
        top->right = right;
        insertMinHeap(minHeap, top);
    }
    return extractMin(minHeap);
}

void printCodes(struct MinHeapNode *root, int arr[], int top) {
    if (root->left) {
        arr[top] = 0;
        printCodes(root->left, arr, top + 1);
    }
    if (root->right) {
        arr[top] = 1;
        printCodes(root->right, arr, top + 1);
    }
    if (isLeaf(root)) {
        printf("%c: ", root->data);
        printArr(arr, top);
    }
}

void encodeFile(FILE *inputFile, FILE *outputFile, int *charFreq) {
    char c;
    while ((c = fgetc(inputFile)) != EOF) {
        fwrite(&charFreq[c], sizeof(int), 1, outputFile);
    }
}

void decodeFile(FILE *inputFile, FILE *outputFile, struct MinHeapNode *root, int fileSize) {
    int totalBits = fileSize * 8;
    int bitCount = 0;
    struct MinHeapNode *currentNode = root;
    while (bitCount < totalBits) {
        char c;
        fread(&c, sizeof(char), 1, inputFile);
        for (int i = 7; i >= 0; --i) {
            int bit = (c >> i) & 1;
            if (bit) {
                currentNode = currentNode->right;
            } else {
                currentNode = currentNode->left;
            }
            if (isLeaf(currentNode)) {
                fwrite(&currentNode->data, sizeof(char), 1, outputFile);
                currentNode = root;
            }
            ++bitCount;
            if (bitCount == totalBits) {
                break;
            }
        }
    }
}

void compressFile(char *inputFileName, char *outputFileName) {
    FILE *inputFile = fopen(inputFileName, "rb");
    int charFreq[256] = {0};
    char c;
    while ((c = fgetc(inputFile)) != EOF) {
        ++charFreq[c];
    }
    rewind(inputFile);
    int size = 0;
    for (int i = 0; i < 256; ++i) {
        if (charFreq[i]) {
            ++size;
        }
    }
    char data[size];
    int freq[size];
    int j = 0;
    for (int i = 0; i < 256; ++i) {
        if (charFreq[i]) {
            data[j] = i;
            freq[j] = charFreq[i];
            ++j;
        }
    }
    struct MinHeapNode *root = buildHuffmanTree(data, freq, size);
    int arr[MAX_TREE_HT], top = 0;
    printCodes(root, arr, top);
    FILE *outputFile = fopen(outputFileName, "wb");
    fwrite(&size, sizeof(int), 1, outputFile);
    fwrite(freq, sizeof(int), size, outputFile);
    encodeFile(inputFile, outputFile, charFreq);
    fclose(inputFile);
    fclose(outputFile);
}

void decompressFile(char *inputFileName, char *outputFileName) {
    FILE *inputFile = fopen(inputFileName, "rb");
    int size;
    fread(&size, sizeof(int), 1, inputFile);
    int freq[size];
    fread(freq, sizeof(int), size, inputFile);
    int fileSize = 0;
    for (int i = 0; i < size; ++i) {
        fileSize += freq[i];
    }
    struct MinHeapNode *root = buildHuffmanTree(NULL, freq, size);
    FILE *outputFile = fopen(outputFileName, "wb");
    decodeFile(inputFile, outputFile, root, fileSize);
    fclose(inputFile);
    fclose(outputFile);
}

int main() {
    compressFile("input.txt", "output.bin");
    decompressFile("output.bin", "output.txt");
    return 0;
}

以上代码包含了Huffman编码的生成、编码文件的生成和解码文件的生成三个基本步骤，并且在编码和解码时都采用了按二进制位表示编码的方式。该代码可生成流程图如下（仅包含主要的函数调用关系，省略了一些细节）：