题解 | #查找兄弟单词#

#include <iostream>
#include <map>
#include <vector>

using namespace std;

map<string,int> mp;

void genOther(string str,int begin){
    if (begin==str.size()) return;
    for (int i = begin; i < str.size(); ++i) {
        swap(str[i],str[begin]);
        mp[str] = 0;
        genOther(str,begin+1);
        swap(str[i],str[begin]);
    }
}

int main(){
    int n,k;
    string x;
    while (cin>>n){
        vector<string> wv(n);
        for (int i = 0; i < n; ++i) {
            cin>>wv[i];
        }
        cin>>x>>k;

        genOther(x,0);

        int count = 0;
        for (int i = 0; i < wv.size(); ++i) {
            if (wv[i].size() != x.size()) continue;
            if (wv[i]!=x && mp.find(wv[i]) != mp.end()){
                mp[wv[i]]++;
                count++;
            }
        }
        string res;
        for(auto it : mp){
            while(it.second--){
                k--;
                if (k==0){
                    res = it.first;
                    break;
                }
            }
        }
        cout<<count<<endl;
        if (!res.empty()) cout<<res<<endl;
    }
    return 0;
}