我被要求在C中创建一个函数，该函数获得了一个int的数组，它的大小和一个代表该排序是否需要上升或下降的角色(0用于上升或其他任何其他char如果下降(，并返回指针数组。如果排序上升，则指针将从INT数组中的最小值到最大值排序。像那样一切都很好，直到指针阵列以零值返回到主。我的意思是，在函数结束和返回数组之前，数组中有值(并且它们也很好地排序(，但是当Main从函数中获取地址时，它就为空。有人熟悉这个问题吗？
谢谢！
#include <stdio.h>
#define SIZE 100
// Functions declaration
int** pointerSort(int* arr, unsigned int size, char ascend_flag);
void sortMerge (int** sortedArr, int left, int right, char ascend_flag);
void mergeSortAscend (int** arr, int left, int middle, int right);
void mergeSortDescend (int** arr, int left, int middle, int right);
void copyAddress(int** addressArray, int* arr, unsigned int size);
int main()
{
int** sortedArr;
int arr[5] = {8,1,7,2,4};
int size = 5;
sortedArr = pointerSort(arr, size, '1');
return 0;
}
// The pointerSort function gets an array, its size and a flag representing "sort by" (ascending, descending)
int** pointerSort(int* arr, unsigned int size, char ascend_flag)
{
// Variables declaration
int* sortedArr[size];
// Copying the addresses of each value in arr to an addresses array
copyAddress(sortedArr, arr, size);
// Sending the array of addresses, its start and end and the ascend_flag to the sortMerge function
sortMerge(sortedArr, 0, size - 1, ascend_flag);
return (sortedArr);
}
void sortMerge (int** sortedArr, int left, int right, char ascend_flag)
{
// Variables declaration
int middle = (left + right) / 2;
// Checking if there are more than one cell
if (left < right)
{
// Splitting the array into two
sortMerge(sortedArr, left, middle, ascend_flag);
sortMerge(sortedArr, middle + 1, right, ascend_flag);
// Checking if the sort requested is ascending or descending
if (ascend_flag != '0')
{
mergeSortAscend(sortedArr, left, middle, right);
}
else
{
mergeSortDescend(sortedArr, left, middle, right);
}
}
}
void mergeSortAscend (int** arr, int left, int middle, int right)
{
int l = left, m = middle + 1, r = right, i = left;
int* temp[SIZE];
while ((l <= middle) && (m <= right))
{
if (*(arr[l]) > *(arr[m]))
{
temp[i] = arr[m];
m++;
}
else
{
temp[i] = arr[l];
l++;
}
i++;
}
if (l <= middle)
{
while (l <= middle)
{
temp[i] = arr[l];
l++;
i++;
}
}
if (m <= right)
{
while (m <= right)
{
temp[i] = arr[m];
m++;
i++;
}
}
for (int k = left; k <= right; k++)
{
arr[k] = temp[k];
}
}
void copyAddress(int** addressArray, int* arr, unsigned int size)
{
int i;
for (i = 0; i < size; i++)
{
addressArray[i] = &(arr[i]);
}
}
void mergeSortDescend (int** arr, int left, int middle, int right)
{
int l = left, m = middle + 1, r = right, i = left;
int* temp[SIZE];
while ((l <= middle) && (m <= right))
{
if (*(arr[l]) <= *(arr[m]))
{
temp[i] = arr[m];
m++;
}
else
{
temp[i] = arr[l];
l++;
}
i++;
}
if (l <= middle)
{
while (l <= middle)
{
temp[i] = arr[l];
l++;
i++;
}
}
if (m <= right)
{
while (m <= right)
{
temp[i] = arr[m];
m++;
i++;
}
}
for (int k = left; k <= right; k++)
{
arr[k] = temp[k];
}
}
int** pointerSort(int* arr, unsigned int size, char ascend_flag)中的int* sortedArr[size];在您的功能返回后立即变得无效，因为它是堆栈分配的自动变量。
您需要永久存储。例如，通过malloc函数在堆上为sortedArr分配内存并返回。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define SIZE 100
// Functions declaration
int** pointerSort(int* arr, unsigned int size, char ascend_flag);
void sortMerge (int** sortedArr, int left, int right, char ascend_flag);
void mergeSortAscend (int** arr, int left, int middle, int right);
void mergeSortDescend (int** arr, int left, int middle, int right);
void copyAddress(int** addressArray, int* arr, unsigned int size);
int main(void)
{
int** sortedArr;
int arr[5] = {8,1,7,2,4};
int size = 5;
int i =0;
sortedArr = pointerSort(arr, size, '1');
if(sortedArr) // memory was allocated
for(i=0; i<5; i++){
printf("%d ", *sortedArr[i]);
}
free(sortedArr);
return 0;
}
// The pointerSort function gets an array, its size and a flag representing "sort by" (ascending, descending)
int** pointerSort(int* arr, unsigned int size, char ascend_flag)
{
// Variables declaration
//int* sortedArr[size];
int ** sortedArr = malloc( sizeof(int *) * size);
if(sortedArr == NULL) return NULL; // no memory
// Copying the addresses of each value in arr to an addresses array
copyAddress(sortedArr, arr, size);
// Sending the array of addresses, its start and end and the ascend_flag to the sortMerge function
sortMerge(sortedArr, 0, size - 1, ascend_flag);
return (sortedArr);
}
void sortMerge (int** sortedArr, int left, int right, char ascend_flag)
{
// Variables declaration
int middle = (left + right) / 2;
// Checking if there are more than one cell
if (left < right)
{
// Splitting the array into two
sortMerge(sortedArr, left, middle, ascend_flag);
sortMerge(sortedArr, middle + 1, right, ascend_flag);
// Checking if the sort requested is ascending or descending
if (ascend_flag != '0')
{
mergeSortAscend(sortedArr, left, middle, right);
}
else
{
mergeSortDescend(sortedArr, left, middle, right);
}
}
}
void mergeSortAscend (int** arr, int left, int middle, int right)
{
int l = left, m = middle + 1, r = right, i = left;
int* temp[SIZE];
while ((l <= middle) && (m <= right))
{
if (*(arr[l]) > *(arr[m]))
{
temp[i] = arr[m];
m++;
}
else
{
temp[i] = arr[l];
l++;
}
i++;
}
if (l <= middle)
{
while (l <= middle)
{
temp[i] = arr[l];
l++;
i++;
}
}
if (m <= right)
{
while (m <= right)
{
temp[i] = arr[m];
m++;
i++;
}
}
for (int k = left; k <= right; k++)
{
arr[k] = temp[k];
}
}
void copyAddress(int** addressArray, int* arr, unsigned int size)
{
int i;
for (i = 0; i < size; i++)
{
addressArray[i] = &(arr[i]);
}
}
void mergeSortDescend (int** arr, int left, int middle, int right)
{
int l = left, m = middle + 1, r = right, i = left;
int* temp[SIZE];
while ((l <= middle) && (m <= right))
{
if (*(arr[l]) <= *(arr[m]))
{
temp[i] = arr[m];
m++;
}
else
{
temp[i] = arr[l];
l++;
}
i++;
}
if (l <= middle)
{
while (l <= middle)
{
temp[i] = arr[l];
l++;
i++;
}
}
if (m <= right)
{
while (m <= right)
{
temp[i] = arr[m];
m++;
i++;
}
}
for (int k = left; k <= right; k++)
{
arr[k] = temp[k];
}
}
测试：
1 2 4 7 8