读取字符串中不同类型的字符个数

#define _CRT_SECURE_NO_WARNINGS
#pragma warning(disable:6031)
#include<stdio.h>
#include<string.h>
int main()
{
	int bigcount = 0;
	int smallcount = 0;
	int num = 0;
	char str[100];
	printf("请输入一串字符串：");
	scanf("%s", str);
	for (int i = 0; i < strlen(str); i++)
	{
		char res = str[i];
		if ('a' <= res && res <= 'z')
		{
			smallcount++;
		}
		 else if ('A' <=res && 'Z' >=res)
		{
			bigcount++;
		}
		 else if ('0' <= res && '9' >= res)
		{
			num++;
		}
		
	}
	printf("大写字符个数为%d 小写字符个数为%d 数字为%d", bigcount, smallcount, num);
	return 0;
}