#include <bits/stdc++.h>
using namespace std;
int main(){
int n, ans = 0; cin >> n;
vector<pair<string,string>> in;
vector<vector<int>> belove(n);
vector<int> love(n);
vector<int> cn(n);
map<string,int> M;
set<int> iR;
queue<int> nobody;
queue<int> sad;
vector<bool> vis(n,false);
if(n & 1){
cout << "-1\n"; return 0;
}
for(int i = 0; i < n; ++i){
string s1, s2; cin >> s1 >> s2;
M[s1] = i;
in.push_back({s1,s2});
}
for(int i = 0; i < n; ++i){
love[M[in[i].first]] = M[in[i].second];
if(in[i].first != in[i].second)belove[M[in[i].second]].push_back(M[in[i].first]);
}
for(int i = 0; i < n; ++i){
if(love[love[i]] == i && love[i] != i)iR.insert(i);
if(love[i] == i){iR.insert(i);ans++;}
cn[i] = belove[i].size();
if(cn[i] == 0)sad.push(i);
}
for(int i = 0; i < n; ++i){
if(love[i] == i || (iR.count(love[i]) && !iR.count(i)))nobody.push(i);
}
while(!nobody.empty() || !sad.empty()){
while(!nobody.empty()){
auto x = nobody.front();
nobody.pop();
if(iR.count(x))continue;
if(belove[x].size()){
iR.insert(x);
iR.insert(belove[x][0]);
cout << x << " " << belove[x][0] << "\n";
ans++;
for(int i = 0; i < (int)belove[x].size(); ++i){
if(!iR.count(belove[x][i]))nobody.push(belove[x][i]);
}
}
}
if(!sad.empty()){
auto x = sad.front();
sad.pop();
if(iR.count(x)){continue;}
if(iR.count(love[x])){ans++; iR.insert(x); continue;}
iR.insert(x);
iR.insert(love[x]);
cout << x << " " << love[x] << "\n";
ans++;
for(int i = 0; i < (int)belove[love[x]].size(); ++i){
if(!iR.count(belove[love[x]][i]))nobody.push(belove[love[x]][i]);
}
cn[love[love[x]]]--;
if(!cn[love[love[x]]]){
sad.push(love[love[x]]);
}
}
}
for(int i = 0; i < n; ++i){
if(!vis[i] && !iR.count(i)){
int last = i;
vis[last] = true;
int cnt = 2;
while(love[last] != i){
cout << i << "\n";
cnt++;
last = love[last];
vis[last] = true;
}
ans+=(cnt+1)>>1;
}
}
cout << ans << "\n";
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Incorrect |
1 ms |
384 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
256 KB |
Output is correct |
2 |
Correct |
1 ms |
256 KB |
Output is correct |
3 |
Incorrect |
1 ms |
256 KB |
Output isn't correct |
4 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Incorrect |
564 ms |
27512 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Incorrect |
1 ms |
384 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |