为什么我的代码在 C 中返回垃圾值

Question

In the below code I want to reverse the array I created the function arrev() & using while loop to do it

#include <stdio.h>
int arrev(int arr[], int revarr[], int N)
{
    int start = 0;
    while (N > 0)
    {
        revarr[start] = arr[N];
        start++;
        N--;
    }
}
int print(int arr[], int N)
{
    for (int i = 0; i < N; i++)
    {
        printf("%d\n", arr[i]);
    }
}
int main()
{
    int arr[10], revarr[10], N;
    scanf("%d", &N);
    printf("Input String:\n");
    for (int i = 0; i < N; i++)
    {
        scanf("%d", &arr[i]);
    }
    arrev(arr, revarr, N);
    printf("Reversed String:\n");
    print(revarr, N);
}

This is my Output
I am entering the following input: 3 1 2 3 And after reversing I am getting the garbage value as output

Answer 1

At least this problem:

Off-by-one indexing

int arrev(int arr[], int revarr[], int N)
{
    int start = 0;
    while (N > 0)
    {
        // revarr[start] = arr[N];
        revarr[start] = arr[N-1];
        start++;
        N--;
    }
}

Answer 2

arr[N] would definitely consist of garbage value.

You need to store arr[N-1] not arr[N]

correct code:

{
    int start = 0;
    N--;
    while (N >= 0)
    {
        revarr[start] = arr[N];
        start++;
        N--;
    }
}

Answer 3

It's an OBO

Change to

while (N > 0)
{
    N--;
    revarr[start] = arr[N];
    start++;
}

Answer 4

This is due to indexing issue, In C array starts with 0 goes till N-1.

In arrev() you need to decrement N before assigning to reverse array. this code will work

int arrev(int arr[], int revarr[], int N)
{
    int start = 0;
 
    while (N > 0)
    { 
        N--;
        printf(" rev array %d\n", revarr[start]);

        printf(" init array %d\n", arr[N]);
       
        revarr[start] = arr[N];
        start++;
        // printf(revarr[start])
      
    }
   }

As a part of best practice, If you're using int as return type, you should use return 0 or use void as return type.

Also if you want to reverse the array, there is an in-place mechanism which can be achieved.

void arrev(int arr[], int start, int end)
{
 //start = 0
// end = sizeof(arr) - 1

    int temp;
    while (start < end)
    {
        temp = arr[start];  
        arr[start] = arr[end];
        arr[end] = temp;
        start++;
        end--;
    }  
}