输入字符，统计个数

#include<stdio.h>
#include<math.h>
#include<string.h>
int main()
{
    char str[1000000];
    int num[30]={0}, t, i, j, k, a;
    while( gets( str ) )
    {
           t = strlen( str );
           int num[30]={0};
           for( i = 0; i < t; i++ )
             {
                   if( str[i] >= 'a' && str[i] <= 'z' )
                         num[ str[i] - 'a' ]++;
             }
               for( i = 0; i < 26; i++ )
                    printf( "%c:%d\n", 'a' + i, num[i] );
               printf( "\n" );
                    

    }
}