알파벳 빈도수 검출

/* count a-z */
 
#include <stdio.h>
 
char str[100];
int a[25];
int i;
 
int main()
{
 
/* initialization a */
for(i = 0 ; i <= 25 ; i++ )
{
a[i] = 0;
}
 
/* print screen */
printf("Please input character string : ");
gets(str);
 
/* scan str */
for(i = 0 ; str[i] ; i++)
if (str[i]>=97 && str[i]<=122)
{
a[str[i]-97]++;
}
 
/* print frequency */
for(i = 0 ; i <= 25 ; i++)
if(a[i])
printf("%c --- %d\n",i+97,a[i]);
 
return 0;
}