暴力破解+sort排序|适合新手

#include <bits/stdc++.h>
using namespace std;
int main()
{
	string s;
	cin>>s;
	int len=s.size();
	string result1,result2,result3,result4;
	for(int i=0;i<len;i++)
	{
		if(s[i]<='z' and s[i]>='a')
		{
			result1=result1+s[i];
		}
	}
	for(int i=0;i<len;i++)
	{
		if(s[i]<='Z' and s[i]>='A')
		{
			result2=result2+s[i];
		}
	}
	for(int i=0;i<len;i++)
	{
		if(s[i]>='0' and s[i]<='9')
		{
			result3=result3+s[i];
		}
	}
	for(int i=0;i<len;i++)
	{
		if(!(s[i]<='z' and s[i]>='a') and !(s[i]<='Z' and s[i]>='A') and !(s[i]<='9' and s[i]>='0'))
		{
			result4=result4+s[i];
		}
	}
    sort(result1.begin(),result1.end());
    sort(result2.begin(),result2.end());
    sort(result3.begin(),result3.end());
    sort(result4.begin(),result4.end());
	cout<<result1<<result2<<result3<<result4;
}

我也是新手