What is wrong with this C program to count the occurences of each vowel?

Question

PROBLEM:

Write a C program that prompts the user to enter a string of characters terminated by ENTER key (i.e. ‘\\n’) and then count the total number of the occurrence o

Answer 1

(just for fun, my answer)

int main(void)
{
    int counter[5] = {0};
    int *i, c;

    printf("Please enter a string terminated by ENTER key:\n");
    while(i = counter, (c = getchar()) != '\n')
    {
        switch(c)
        {
          default: continue;
          case 'U'+' ': case 'U': ++ i;
          case 'O'+' ': case 'O': ++ i;
          case 'I'+' ': case 'I': ++ i;
          case 'E'+' ': case 'E': ++ i;
          case 'A'+' ': case 'A': ++*i;
        }
    }

    for(c = 0; c < 5;

    printf("counter[%d] = %d\n", c, counter[c++]));

    return 0;
}