https://old.517coding.com/p/1320

#include<bits/stdc++.h>
using namespace std;
char s[55];
int main(){
	gets(s);
	int len=strlen(s);
	for(int i=0;i<len;i++){
		if(s[i]!=0&&s[i]>='A'&&s[i]<='Z'){
			if(s[i]>='A'&&s[i]<='W'){
				s[i]+=3+32;
			}else{
				s[i]-=23-32;
			}
		}
		if(s[i]!=0&&s[i]>='a'&&s[i]<='z'){
			if(s[i]>='a'&&s[i]<='w'){
				s[i]=s[i]+3-32;
			}else{
				s[i]=s[i]-23-32;
			}
		}
	}
	puts(s);
	return 0;
}

为什么大写变小写会出问题