#include<bits/stdc++.h> using namespace std; int main(){ char a; cin>>a; if(a=='a'){ cout<<"A"; } if(a=='A'){ cout<<"a"; } if(a=='b'){ cout<<"B"; } if(a=='B'){ cout<<"b"; } if(a=='c'){ cout<<"C"; } if(a=='C'){ cout<<"c"; } if(a=='d'){ cout<<"D"; } if(a=='D'){ cout<<"d"; } if(a=='e'){ cout<<"E"; } if(a=='E'){ cout<<"e"; } if(a=='f'){ cout<<"F"; } if(a=='F'){ cout<<"f"; } if(a=='g'){ cout<<"G"; } if(a=='G'){ cout<<"g"; } if(a=='h'){ cout<<"H"; } if(a=='H'){ cout<<"h"; } if(a=='i'){ cout<<"I"; } if(a=='I'){ cout<<"i"; } if(a=='j'){ cout<<"J"; } if(a=='J'){ cout<<"j"; } if(a=='k'){ cout<<"K"; }if(a=='K'){ cout<<"k"; } if(a=='l'){ cout<<"L"; } if(a=='L'){ cout<<"l"; } if(a=='m'){ cout<<"M"; } if(a=='M'){ cout<<"m"; } if(a=='n'){ cout<<"N"; } if(a=='N'){ cout<<"n"; } if(a=='o'){ cout<<"O"; } if(a=='O'){ cout<<"o"; } if(a=='p'){ cout<<"P"; } if(a=='P'){ cout<<"p"; } if(a=='q'){ cout<<"Q"; } if(a=='Q'){ cout<<"q"; } if(a=='r'){ cout<<"R"; } if(a=='R'){ cout<<"r"; } if(a=='s'){ cout<<"S"; } if(a=='S'){ cout<<"s"; } if(a=='t'){ cout<<"T"; } if(a=='T'){ cout<<"t"; } if(a=='u'){ cout<<"U"; } if(a=='U'){ cout<<"u"; } if(a=='v'){ cout<<"V"; } if(a=='V'){ cout<<"v"; } if(a=='w'){ cout<<"W"; } if(a=='W'){ cout<<"w"; } if(a=='x'){ cout<<"X"; } if(a=='X'){ cout<<"x"; } if(a=='y'){ cout<<"Y"; } if(a=='Y'){ cout<<"y"; } if(a=='z'){ cout<<"Z"; } if(a=='Z'){ cout<<"z"; } return 0; }

#include<bits/stdc++.h>
using namespace std;
int main(){
	char a;
	cin>>a;
	if(a=='a'){
		cout<<"A";
	}
	if(a=='A'){
		cout<<"a";
	}
	if(a=='b'){
		cout<<"B";
	}
	if(a=='B'){
		cout<<"b";
	}
	if(a=='c'){
		cout<<"C";
	}
	if(a=='C'){
		cout<<"c";
	}
	if(a=='d'){
		cout<<"D";
	}
	if(a=='D'){
		cout<<"d";
	}
	if(a=='e'){
		cout<<"E";
	}
	if(a=='E'){
		cout<<"e";
	}
	if(a=='f'){
		cout<<"F";
	}
	if(a=='F'){
		cout<<"f";
	}
	if(a=='g'){
		cout<<"G";
	}
	if(a=='G'){
		cout<<"g";
	}
	if(a=='h'){
		cout<<"H";
	}
	if(a=='H'){
		cout<<"h";
	}
	if(a=='i'){
		cout<<"I";
	}
	if(a=='I'){
		cout<<"i";
	}
	if(a=='j'){
		cout<<"J";
	}
	if(a=='J'){
		cout<<"j";
	}
	if(a=='k'){
		cout<<"K";
	}if(a=='K'){
		cout<<"k";
	}
	if(a=='l'){
		cout<<"L";
	}
	if(a=='L'){
		cout<<"l";
	}
	if(a=='m'){
		cout<<"M";
	}
	if(a=='M'){
		cout<<"m";
	}
	if(a=='n'){
		cout<<"N";
	}
    if(a=='N'){
		cout<<"n";
	}
	if(a=='o'){
		cout<<"O";
	}
	if(a=='O'){
		cout<<"o";
	}
	if(a=='p'){
		cout<<"P";
	}
	if(a=='P'){
		cout<<"p";
	}
	if(a=='q'){
		cout<<"Q";
	}
	if(a=='Q'){
		cout<<"q";
	}
	if(a=='r'){
		cout<<"R";
	}
	if(a=='R'){
		cout<<"r";
	}
	if(a=='s'){
		cout<<"S";
	}
	if(a=='S'){
		cout<<"s";
	}
	if(a=='t'){
		cout<<"T";
	}
	if(a=='T'){
		cout<<"t";
	}
	if(a=='u'){
		cout<<"U";
	}
	if(a=='U'){
		cout<<"u";
	}
	if(a=='v'){
		cout<<"V";
	}
	if(a=='V'){
		cout<<"v";
	}
	if(a=='w'){
		cout<<"W";
	}
	if(a=='W'){
		cout<<"w";
	}
	if(a=='x'){
		cout<<"X";
	}
	if(a=='X'){
		cout<<"x";
	}
	if(a=='y'){
		cout<<"Y";
	}
	if(a=='Y'){
		cout<<"y";
	}
	if(a=='z'){
		cout<<"Z";
	}
	if(a=='Z'){
		cout<<"z";
	}
	return 0;
}

我长不长？

using namespace std;
int main(){
	char a;
	cin>>a;
	if(a=='a'){
		cout<<"A";
	}
	if(a=='A'){
		cout<<"a";
	}
	if(a=='b'){
		cout<<"B";
	}
	if(a=='B'){
		cout<<"b";
	}
	if(a=='c'){
		cout<<"C";
	}
	if(a=='C'){
		cout<<"c";
	}
	if(a=='d'){
		cout<<"D";
	}
	if(a=='D'){
		cout<<"d";
	}
	if(a=='e'){
		cout<<"E";
	}
	if(a=='E'){
		cout<<"e";
	}
	if(a=='f'){
		cout<<"F";
	}
	if(a=='F'){
		cout<<"f";
	}
	if(a=='g'){
		cout<<"G";
	}
	if(a=='G'){
		cout<<"g";
	}
	if(a=='h'){
		cout<<"H";
	}
	if(a=='H'){
		cout<<"h";
	}
	if(a=='i'){
		cout<<"I";
	}
	if(a=='I'){
		cout<<"i";
	}
	if(a=='j'){
		cout<<"J";
	}
	if(a=='J'){
		cout<<"j";
	}
	if(a=='k'){
		cout<<"K";
	}if(a=='K'){
		cout<<"k";
	}
	if(a=='l'){
		cout<<"L";
	}
	if(a=='L'){
		cout<<"l";
	}
	if(a=='m'){
		cout<<"M";
	}
	if(a=='M'){
		cout<<"m";
	}
	if(a=='n'){
		cout<<"N";
	}
    if(a=='N'){
		cout<<"n";
	}
	if(a=='o'){
		cout<<"O";
	}
	if(a=='O'){
		cout<<"o";
	}
	if(a=='p'){
		cout<<"P";
	}
	if(a=='P'){
		cout<<"p";
	}
	if(a=='q'){
		cout<<"Q";
	}
	if(a=='Q'){
		cout<<"q";
	}
	if(a=='r'){
		cout<<"R";
	}
	if(a=='R'){
		cout<<"r";
	}
	if(a=='s'){
		cout<<"S";
	}
	if(a=='S'){
		cout<<"s";
	}
	if(a=='t'){
		cout<<"T";
	}
	if(a=='T'){
		cout<<"t";
	}
	if(a=='u'){
		cout<<"U";
	}
	if(a=='U'){
		cout<<"u";
	}
	if(a=='v'){
		cout<<"V";
	}
	if(a=='V'){
		cout<<"v";
	}
	if(a=='w'){
		cout<<"W";
	}
	if(a=='W'){
		cout<<"w";
	}
	if(a=='x'){
		cout<<"X";
	}
	if(a=='X'){
		cout<<"x";
	}
	if(a=='y'){
		cout<<"Y";
	}
	if(a=='Y'){
		cout<<"y";
	}
	if(a=='z'){
		cout<<"Z";
	}
	if(a=='Z'){
		cout<<"z";
	}
	return 0;
}

直接判断输出。

#include<bits/stdc++.h>
#define int long long
#define INF 0x3f3f3f
using namespace std;
char c;
signed main(){
	cin>>c;
	if(c>='a')cout<<char(c-32);
	else cout<<char(c+32);
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
signed main(){
	char a;
	cin>>a;
	if(isupper(a))cout<<char(a+32);
	else cout<<char(a-32);
}