递归检查数组是否按偶数索引排序

Question

我正在尝试编写一个递归函数来检查给定数组是否在偶数索引上向上排序。例如我有一个 size 5 的数组.数字是1 , 2 , 3 , 4 ,5 .它将return 1因为arr[0] < arr[2] < arr[4] .

那条线上的问题:

if (i >= arr[isEven]) return 1; //Sorted

代码如下:

#include <stdio.h>
#include <conio.h>

int SortedUpDown(int arr, int num);

int main()
{
    int sizeOfArr = 0, i = 0,*arr, num = 0, checkIfSorted = -1;
    printf("Enter the size of the array : \n");
    scanf("%d", &sizeOfArr);
    printf("Enter %d numbers to the array \n: ", sizeOfArr);
    arr = (int *)malloc(sizeOfArr * sizeof(int));
    for (i = 0; i < sizeOfArr; i++)
    {
        scanf("%d", &num);
        *(arr + i) = num;
        printf("%d ", arr[i]);
    }
    checkIfSorted = SortedUpDown(*arr,sizeOfArr);
    getch();

    return 0;
}

int SortedUpDown(int *arr, int num)
{
    int i = 0, isEven = 0;
    if (num % 2 == 0) isEven = num - 2; //if The array is even, (for example arr[6] then check 0,1,2,3,4,5 only 0,2,4)
    else isEven = num - 1; //if the array is odd, (for example arr[7] then check 0,1,2,3,4,5,6 only 0,2,4,6)
    if (i >= arr[isEven]) return 1; //Sorted
    if (arr[i] > arr[i + 2]) return 0; //Not sorted
    return i += 2, SortedUpDown(arr, num); //Advance i by 2.
}

抛出的错误:

Exception thrown at 0x00AE18BC in ConsoleApplication1.exe: 0xC0000005: Access violation reading location 0x00000011.

If there is a handler for this exception, the program may be safely continued.

编辑:我现在想检查它是否针对奇数索引向下并且它不起作用，这是我的代码:

我有两个问题:

1. 为什么它不起作用？

   1. 你能帮我把这 2 个函数写在一个函数中吗，也就是说，它会同时检查偶数索引上的 Up 和奇数索引上的 Down？

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

int SortedDown(int *arr, int num); 
int SortedUp(int *arr, int num);

int main(void)
{
  int sizeOfArr = 0, i = 0, *arr, num = 0, checkIfSortedDown = -1, checkIfSortedUp = -1;
  printf("Enter the size of the array : \n");
  scanf("%d", &sizeOfArr);
  printf("Enter %d numbers to the array \n: ", sizeOfArr);
  arr = (int *)malloc(sizeOfArr * sizeof(int));
  for (i = 0; i < sizeOfArr; i++)
  {
      scanf("%d", arr + i);
      printf("%d ", arr[i]);
  }
  puts("");
  checkIfSortedDown = SortedDown(arr, sizeOfArr);
  checkIfSortedUp = SortedUp(arr, sizeOfArr);
  if (checkIfSortedDown && checkIfSortedUp)
      puts("Sorted");
  else
      puts("Not Sorted");
  free(arr);
  getch();

  return 0;
}

int SortedDown(int *arr, int num) {
  --num;//size to last index
  if (num % 2 != 0) //if index is not even
      --num;
  if (num <= 0)
      return 1;//Sorted
  else if (arr[num - 2] > arr[num])
      return 0;//Not sorted
  else
      return SortedDown(arr, num - 2 + 1);//+1 : last index to size
}

int SortedUp(int *arr, int num) {
  --num;//size to last index
  if (num % 2 == 0)
      --num;
  if (num <= 0)
      return 1;//Sorted
  else if (arr[num - 2] < arr[num])
      return 0;//Not sorted
  else
      return SortedUp(arr, num - 2 + 1);//+1 : last index to size
}

Answer 1

#include <stdio.h>
#include <stdlib.h> //need this header
#include <conio.h>  //not standard

int SortedUpDown(int *arr, int num);//prototype to match implementation 

int main(void)
{
    int sizeOfArr = 0, i = 0, *arr, num = 0, checkIfSorted = -1;
    printf("Enter the size of the array : \n");
    scanf("%d", &sizeOfArr);
    printf("Enter %d numbers to the array \n: ", sizeOfArr);
    arr = (int *)malloc(sizeOfArr * sizeof(int));
    for (i = 0; i < sizeOfArr; i++)
    {
        scanf("%d", arr + i);
        printf("%d ", arr[i]);
    }
    puts("");
    checkIfSorted = SortedUpDown(arr, sizeOfArr);//pass arr, not *arr
    if(checkIfSorted)
        puts("Sorted");
    else
        puts("Not Sorted");
    free(arr);
    getch();

    return 0;
}

int SortedUpDown(int *arr, int num){
    --num;//size to last index
    if (num % 2 != 0)
        --num;
    if(num <= 0)
        return 1;//Sorted
    else if (arr[num-2] > arr[num])
        return 0;//Not sorted
    else
        return SortedUpDown(arr, num-2+1);//+1 : last index to size
}