从数组中删除一个元素

Question

I was trying to delete an element from an array, I have succeeded, but I got unknown numbers (0 1804185664) after deleting an element from array.

Can someone help me out why did that appear?

#include <stdio.h>
#include <stdlib.h>
int main()
{
    int arr[30];
    int n,i,pos;
    
    printf("how many ele\n");
    scanf("%d", &n);
    printf("enter %d ele\n",n);
    for(i=0;i<n;i++)
    {
      scanf("%d", &a[i]);
    }
    
    printf("enter position of element to be deleted\n");
    scanf("%d", &pos);
    for(i=pos-1; i<=n;i++)
    {
      a[i]= a[i+1];
    }
    printf("elements in array are\n");
    for(i=0; i<=n;i++)
    {
      printf("%d\t", a[i]);
    }
    return 0;
}

Output:

how many ele
7
enter 7 ele
1
5
34
6
23
78
5
enter position of element to be deleted
3
elements in array are
1   5   6   23  78  5   0   1804185664  

Answer 1

I modified your code, and as they were saying in the comments for your question, the problem is that you were accessing elements outside you array range, also there is one more thing with you code is the what if you want to delete the last element in the array, how would you delete it? , instead of shifting all elements of the array, you can put the maximum/minimum value of integer in the place you are deleting so that you come back to that place, you will know this place was deleted before. this will decrease the time of deletion (O(1))but it will increase the time of insertion (O(N)), wile you code is based on increasing the time of deletion (O(n)) but it decreases the time of insertion (O(1)) this is your modified code based on shifting on deletion:

#include <stdio.h>
#include <stdlib.h>
int main()
{
   int arr[30];
   int n, i, pos;

   printf("how many ele\n");
   scanf_s("%d", &n);
   printf("enter %d ele\n", n);
   for (i = 0; i < n; i++)
   {
       scanf_s("%d", &arr[i]);
   }

   printf("enter position of element to be deleted\n");
   scanf_s("%d", &pos);
   for (i = pos - 1; i < n - 1; i++)
   {
       arr[i] = arr[i + 1];
   }
   printf("elements in array are\n");
   for (i = 0; i < n; i++)
   {
        printf("%d\t", arr[i]);
   }
   return 0;
}