Question

这是我的代码。我对c和指针都很陌生，所以可能是指针上的错误。

#include<stdio.h>
#include <stdbool.h>

typedef int (*comparatorPtr)(void*, void*);
bool isMaxHeap(void **heap, int index, int length, comparatorPtr comparator);

/**
 * comparator with pointers (the mistake could be here)
 */
int comparator_integer(void* e1, void* e2) {
  int i1 = *(int *) e1;
  int i2 = *(int *) e2;

  //print 2 elements of array/heap
  printf("I1 heap: %d\n", i1);
  printf("I2 heap: %d\n", i2);
  printf("***************************\n");

  if (i1 == i2) return 0;
  else if (i1 > i2) return 1;
  else return -1;
}

/**
 * Function for check if the array is or isn't a maxHeap
 */
bool isMaxHeap(void **heap, int index, int length, comparatorPtr comparator) {
  if (index > length - 1) return true;

  printf("I'm calling comparator 1 \n%d value index1\n",index);
  if (length > index * 2 && comparator((heap + index), (heap + (index * 2))) < 0) return false;

  printf("I'm calling comparator 2 \n%d value index2\n",index);
  printf("Value lenght %d\n", length);
  if (length > index * 2 + 1 && comparator((heap + index), (heap + ((index * 2) + 1))) < 0) return false;

  printf("I'm calling comparator 3 \n");
  if (index == 0) return isMaxHeap(heap, 1, length, comparator) && isMaxHeap(heap, 2, length, comparator);

  else return isMaxHeap(heap, index * 2, length, comparator) && isMaxHeap(heap, index * 2 + 1, length, comparator);
}

int main() {
  int array[6] = {90, 15, 10, 7, 12, 2}; //maxHeap array
  int length = sizeof(array)/ sizeof(array[0]);
  int index = 0;

  printf("element in position 1: %d\n",*(array + (index*2)+1));
  printf("length %d\n", length);

  isMaxHeap((void **) &array, index, length, &comparator_integer) ? printf("Yes"): printf("No");
return 0;
}

数组是MaxHeap，但我不知道为什么我的代码返回No. （printf仅用于尝试捕获错误）

由于

Answer 1

你不应该将数组转换为void **。如果你有一个指针数组，那么这是合适的，但你只有一个数据数组。

您需要将每个数组元素的大小传递给函数。然后，该函数需要将数组指针强制转换为char *以访问数组元素。它需要将大小乘以数组索引以获得它传递给比较器函数的数组元素的offsdet（这是在索引类型化数组时自动发生的情况，但是你必须在函数中模拟它，因为它＆＃39;在通用阵列上运行。）

您还在为子节点使用错误的索引。左边的孩子在index * 2 + 1，右边的孩子在index * 2 + 2。

在最后进行递归调用时，index == 0无需特殊情况。

在调用&array时，您不需要使用isMaxHeap()，因为当用作函数参数时，数组会自动衰减为指针。

#include<stdio.h>
#include <stdbool.h>

typedef int (*comparatorPtr)(void*, void*);
bool isMaxHeap(void *heap, int index, int length, size_t size, comparatorPtr comparator);

/**
 * comparator with pointers (the mistake could be here)
 */
int comparator_integer(void* e1, void* e2) {
    int i1 = *(int *) e1;
    int i2 = *(int *) e2;

    //print 2 elements of array/heap
    printf("I1 heap: %d\n", i1);
    printf("I2 heap: %d\n", i2);
    printf("***************************\n");

    if (i1 == i2) return 0;
    else if (i1 > i2) return 1;
    else return -1;
}

/**
 * Function for check if the array is or isn't a maxHeap
 */
bool isMaxHeap(void *heap, int index, int length, size_t size, comparatorPtr comparator) {
    char *heapbase = heap;
    if (index >= length) {
        return true;
    }

    printf("I'm calling comparator 1 \n%d value index1\n",index);
    if (length > index * 2 + 1 && comparator(heapbase + index * size, heapbase + (index * 2 + 1) * size) < 0) {
        return false;
    }

    printf("I'm calling comparator 2 \n%d value index2\n",index);
    printf("Value lenght %d\n", length);
    if (length > index * 2 + 2 && comparator(heapbase + index * size, heapbase + (index * 2 + 2) * size) < 0) {
        return false;
    }

    printf("I'm calling comparator 3 \n");
    return isMaxHeap(heap, index * 2 + 1, length, size, comparator) && isMaxHeap(heap, index * 2 + 2, length, size, comparator);
}

int main() {
    int array[6] = {90, 15, 10, 7, 12, 2}; //maxHeap array
    int length = sizeof(array)/ sizeof(array[0]);
    int index = 0;

    printf("element in position 1: %d\n",*(array + (index*2)+1));
    printf("length %d\n", length);

    isMaxHeap(array, index, length, sizeof array[0], comparator_integer) ? printf("Yes\n"): printf("No\n");
    return 0;
}

检查泛型类型数组是否为MaxHeap的算法

1 个答案: