C语言实现统计字符类型：字母、数字、空格和其他字符

#include<stdio.h>
int main()
{
    char str[100];
    int i, letter = 0, digit = 0, space = 0, other = 0;
    printf('请输入一行字符：');
    gets(str);
    for(i=0; str[i]!='\0'; i++)
    {
        if((str[i]>='a' && str[i]<='z') || (str[i]>='A' && str[i]<='Z'))
            letter++;
        else if(str[i]>='0' && str[i]<='9')
            digit++;
        else if(str[i]==' ')
            space++;
        else
            other++;
    }
    printf('字母个数：%d\n数字个数：%d\n空格个数：%d\n其他字符个数：%d\n', letter, digit, space, other);
    return 0;
}