python/TangDou/CSP-J/AcWingTraining/T6/me.cpp

#include <bits/stdc++.h>

using namespace std;
const int N = 20;
char s[N];
int len;
void dfs(int u,string t){
    if(u==len){
        cout << t << endl;
        return;
    }
    if(s[u]>='A'&&s[u]<='Z'){
        dfs(u + 1, t + s[u]);
        string tmp;
        tmp.push_back(s[u] + 32);
        dfs(u + 1, t + tmp);
    }else if(s[u]>='a'&&s[u]<='z'){
        string tmp;
        tmp.push_back(s[u] - 32);
        dfs(u + 1, t + tmp);
        dfs(u + 1, t + s[u]);
    }else
        dfs(u + 1, t + s[u]);
}
int main() {
    cin >> s;
    len = strlen(s);
    dfs(0, "");
    return 0;
}