huffman编码c语言

Huffman编码是一种用于数据压缩的算法，它通过根据字符出现的频率构建一棵哈夫曼树，并根据树的路径为每个字符分配一个唯一的编码。

以下是一个示例的Huffman编码的C语言实现：

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

#define MAX_TREE_HT 100

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

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

struct MinHeapNode* createNode(char data, unsigned frequency) {
    struct MinHeapNode* node = (struct MinHeapNode*) malloc(sizeof(struct MinHeapNode));
    node->left = node->right = NULL;
    node->data = data;
    node->frequency = frequency;
    return node;
}

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]->frequency < minHeap->array[smallest]->frequency) {
        smallest = left;
    }

    if (right < minHeap->size && minHeap->array[right]->frequency < minHeap->array[smallest]->frequency) {
        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->frequency < minHeap->array[(i - 1) / 2]->frequency) {
        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 frequency[], int size) {
    struct MinHeap* minHeap = createMinHeap(size);

    for (int i = 0; i < size; ++i) {
        minHeap->array[i] = createNode(data[i], frequency[i]);
    }

    minHeap->size = size;
    buildMinHeap(minHeap);

    return minHeap;
}

struct MinHeapNode* buildHuffmanTree(char data[], int frequency[], int size) {
    struct MinHeapNode *left, *right, *top;
    struct MinHeap* minHeap = createAndBuildMinHeap(data, frequency, size);

    while (!isSizeOne(minHeap)) {
        left = extractMin(minHeap);
        right = extractMin(minHeap);
        top = createNode('$', left->frequency + right->frequency);
        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 huffmanCodes(char data[], int frequency[], int size) {
    struct MinHeapNode* root = buildHuffmanTree(data, frequency, size);
    int arr[MAX_TREE_HT], top = 0;
    printCodes(root, arr, top);
}

int main() {
    char data[] = {'a', 'b', 'c', 'd', 'e', 'f'};
    int frequency[] = {5, 9, 12, 13, 16, 45};
    int size = sizeof(data) / sizeof(data[0]);
    huffmanCodes(data, frequency, size);
    return 0;
}

这个示例程序中，我们首先定义了哈夫曼树的数据结构和相关的操作函数。然后，我们创建了一个包含字符及其出现频率的数组，并使用它们构建了哈夫曼树。最后，我们打印了每个字符对应的编码。

请注意，此示例程序仅用于演示Huffman编码的基本实现原理，实际应用中可能需要进行更多的错误处理和优化。