无法释放 C 中的所有内存

Question

我正在使用最小堆对整数数组进行霍夫曼编码。我的问题是在我将霍夫曼代码打印到屏幕后释放 MinHeap 和 MinHeapNodes。每当我调用 "printCodes" 时，我都会释放 minHeap 的叶节点，但我仍然无法释放非叶节点以及 MinHeap 和 MinHeap 的数组。

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

#define MAX_TREE_HT 100

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

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

struct MinHeapNode *newNode(int 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 *tmp = *a;
        *a = *b;
        *b = tmp;
}
void minHeapify(struct MinHeap *minHeap, int index) {
        int smallest = index;
        int left = 2 * index + 1;
        int right = 2 * index + 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 != index) {
                swapMinHeapNode(&minHeap->array[smallest], &minHeap->array[index]);
                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(int data[], int freq[], int size) {
        struct MinHeap *minHeap = createMinHeap(size);
        int i;
        for (i = 0; i < size; i++)
                minHeap->array[i] = newNode(data[i], freq[i]);
        minHeap->size = size;
        buildMinHeap(minHeap);
        return minHeap;
}

struct MinHeapNode *buildHuffmanTree(int data[], int freq[], int size, struct MinHeap *clear) {
        struct MinHeapNode *left, *right, *top;
        struct MinHeap *minHeap = createAndBuildMinHeap(data, freq, size);
        while (!isSizeOne(minHeap)) {
                left = extractMin(minHeap);
                right = extractMin(minHeap);
                top = newNode(255, left->freq + right->freq);
                top->left = left;
                top->right = right;
                insertMinHeap(minHeap, top);
        }
        clear = minHeap;
        //clear->array = minHeap->array
        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("%d: ", root->data);
                printArr(arr, top);
                free(root);
        }
}
void HuffmanCodes(int data[], int freq[], int size) {
        struct MinHeap *clear;
        struct MinHeapNode *root = buildHuffmanTree(data, freq, size, clear);
        int arr[MAX_TREE_HT], top = 0;
        printCodes(root, arr, top);
        //free(clear->array); Adding this will crash the program
        //free(clear);
        free(root);
}
int main() {
        int arr[] = {3, 4, 5};
        int freq[] = {1, 4, 5};
        int size = sizeof(arr) / sizeof(arr[0]);
        HuffmanCodes(arr, freq, size);
        return 0;
}

Answer 1

为了便于阅读，我会重命名您的 printCodes 函数 printCodesAndFree。
我猜，你会挠头然后撞到墙上。您正在将 clear 指针按值传递给 createAndBuildMinHeap 并设置局部变量。您应该传递 &clear 并在 buildHuffmanTree 中接收参数 struct MinHeap** clear，然后设置 *clear = minHeap。我想这会解决您的问题。

无法释放 C 中的所有内存

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