在循环中使用scanf的程序打印不正确的输出

Question

I don't know what's happening with this code.

#include<stdio.h>
int main()
   {
   int ii[5], i;
   for (i=1; i<=5; i++)
   {
      scanf("%d", &ii[i]);
   }
   printf("----------------------\n");  
   for(i=1; i<=5; i++)
   printf("%d\n", ii[i]);
   return 0;
   }

After compiling when I provide input as

1 2 3 4 5

then it prints as it is, but when I provide input in reverse order:

5 4 3 2 1

it keeps on asking up to some more digits and after that it prints out some random digits from given set of input.

How can I fix this?

Answer 1

c uses 0 indexing that means that array indexes start at 0 not 1. A for loop over an array should look like this:

int array[ARRAY_LENGTH], i;
for (i = 0; i < ARRAY_LENGTH; ++i) {

This will ensure that i will go from 0 to ARRAY_LENGTH - 1 and will not go outside the bounds of your array.

These lines:

for(i=1; i<=5; i++)
printf("%d\n", ii[i]);

will Access element 5 of ii where the maximum index is 4. This will cause Undefined Behavior which is likely why you are seeing random numbers appear.