#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T, typename U> using ordered_map = tree<T, U, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long ll;
typedef long double ld;
typedef double db;
typedef string str;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<str> vstr;
#define FOR(i,j,k,in) for(int i=(j); i < (k);i+=in)
#define FORD(i,j,k,in) for(int i=(j); i >=(k);i-=in)
#define REP(i,b) FOR(i,0,b,1)
#define REPD(i,b) FORD(i,b,0,1)
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define all(x) begin(x), end(x)
#define rsz resize
#define MANY_TESTS int tcase; cin >> tcase; while(tcase--)
const double EPS = 1e-9;
const int MOD = 1e9+7; // 998244353;
const ll INFF = 1e18;
const int INF = 1e9;
const ld PI = acos((ld)-1);
const vi dy = {1, 0, -1, 0, -1, 1, 1, -1};
const vi dx = {0, 1, 0, -1, -1, 1, -1, 1};
#ifdef DEBUG
#define DBG if(1)
#else
#define DBG if(0)
#endif
#define dbg(x) cout << "(" << #x << " : " << x << ")" << endl;
// ostreams
template <class T, class U>
ostream& operator<<(ostream& out, const pair<T, U> &par) {out << "[" << par.first << ";" << par.second << "]"; return out;}
template <class T>
ostream& operator<<(ostream& out, const set<T> &cont) { out << "{"; for( const auto &x:cont) out << x << ", "; out << "}"; return out; }
template <class T, class U>
ostream& operator<<(ostream& out, const map<T, U> &cont) {out << "{"; for( const auto &x:cont) out << x << ", "; out << "}"; return out; }
template<class T>
ostream& operator<<(ostream& out, const vector<T> &v){ out << "["; REP(i, v.size()) out << v[i] << ", "; out << "]"; return out;}
// istreams
template<class T>
istream& operator>>(istream& in, vector<T> &v){ for(auto &x : v) in >> x; return in; }
template<class T, class U>
istream& operator>>(istream& in, pair<T, U> &p){ in >> p.ff >> p.ss; return in; }
//searches
template<typename T, typename U>
T bsl(T lo, T hi, U f){ hi++; T mid; while(lo < hi){ mid = (lo + hi)/2; f(mid) ? hi = mid : lo = mid+1; } return lo; }
template<typename U>
double bsld(double lo, double hi, U f, double p = 1e-9){ int r = 3 + (int)log2((hi - lo)/p); double mid; while(r--){ mid = (lo + hi)/2; f(mid) ? hi = mid : lo = mid; } return (lo + hi)/2; }
template<typename T, typename U>
T bsh(T lo, T hi, U f){ lo--; T mid; while(lo < hi){ mid = (lo + hi + 1)/2; f(mid) ? lo = mid : hi = mid-1; } return lo; }
template<typename U>
double bshd(double lo, double hi, U f, double p = 1e-9){ int r = 3+(int)log2((hi - lo)/p); double mid; while(r--){ mid = (lo + hi)/2; f(mid) ? lo = mid : hi = mid; } return (lo + hi)/2; }
// some more utility functions
template<typename T>
pair<T, int> get_min(vector<T> &v){ typename vector<T> :: iterator it = min_element(v.begin(), v.end()); return mp(*it, it - v.begin());}
template<typename T>
pair<T, int> get_max(vector<T> &v){ typename vector<T> :: iterator it = max_element(v.begin(), v.end()); return mp(*it, it - v.begin());}
template<typename T> bool ckmin(T& a, const T& b){return b < a ? a = b , true : false;}
template<typename T> bool ckmax(T& a, const T& b){return b > a ? a = b, true : false;}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int n; cin >> n;
if(n % 2 == 1){
cout << -1 << "\n";
return 0;
}
vector<int> g(n);
int curr_id = 0;
map<string, int> name_to_id;
REP(i, n){
string s, t;
cin >> s >> t;
int u, v;
if(name_to_id.find(s) == name_to_id.end())
name_to_id[s] = curr_id++;
if(name_to_id.find(t) == name_to_id.end())
name_to_id[t] = curr_id++;
u = name_to_id[s];
v = name_to_id[t];
g[u] = v;
}
vector<int> cycle_begins;
vector<int> visited(n, -1);
function<void(int, int, bool)> dfs = [&](int v, int id, bool cycle_finding){
visited[v] = id;
if(visited[g[v]] == -1)
dfs(g[v], id, cycle_finding);
else{
if(visited[g[v]] == visited[v] && cycle_finding)
cycle_begins.pb(v);
}
};
int cid = 0;
REP(i, n){
if(visited[i] == -1){
dfs(i, cid, true);
cid++;
}
}
fill(all(visited), -1);
cid = 0;
REP(i, cycle_begins.size()){
if(visited[cycle_begins[i]] == -1){
dfs(cycle_begins[i], cid, false);
cid++;
}
}
int cycle_ids = cid;
vector<int> chain_begins;
vector<int> indeg(n, 0);
REP(i, n){
indeg[g[i]]++;
}
REP(i, n){
if(indeg[i] == 0) chain_begins.pb(i);
}
REP(i, chain_begins.size()){
if(visited[chain_begins[i]] == -1){
dfs(chain_begins[i], cid, false);
cid++;
}
}
int res = 0;
vi cnt(n, 0);
vi paired(n, 0);
REP(i, n){
cnt[visited[i]]++;
}
vi compressed_g(n, -1);
REP(i, n){
if(visited[g[i]] != visited[i]){
compressed_g[visited[i]] = visited[g[i]];
}
}
REP(i, n){
if(cnt[i] == 2 && i < cycle_ids) continue;
if(cnt[i] % 2 == 0) res += cnt[i] / 2;
else{
res += cnt[i] / 2 + 1;
}
}
REP(i, n){
if(cnt[i] % 2 == 1 && compressed_g[i] != -1){
if(cnt[compressed_g[i]] % 2 == 1){
if(!paired[compressed_g[i]]){
paired[compressed_g[i]] = true;
res--;
}
}
}
}
cout << res << "\n";
return 0;
}
Compilation message
polygon.cpp: In function 'int main()':
polygon.cpp:26:40: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
26 | #define FOR(i,j,k,in) for(int i=(j); i < (k);i+=in)
| ^
polygon.cpp:28:18: note: in expansion of macro 'FOR'
28 | #define REP(i,b) FOR(i,0,b,1)
| ^~~
polygon.cpp:128:5: note: in expansion of macro 'REP'
128 | REP(i, cycle_begins.size()){
| ^~~
polygon.cpp:26:40: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
26 | #define FOR(i,j,k,in) for(int i=(j); i < (k);i+=in)
| ^
polygon.cpp:28:18: note: in expansion of macro 'FOR'
28 | #define REP(i,b) FOR(i,0,b,1)
| ^~~
polygon.cpp:143:5: note: in expansion of macro 'REP'
143 | REP(i, chain_begins.size()){
| ^~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
364 KB |
Output is correct |
| 2 |
Correct |
1 ms |
364 KB |
Output is correct |
| 3 |
Incorrect |
1 ms |
364 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
364 KB |
Output is correct |
| 2 |
Correct |
1 ms |
364 KB |
Output is correct |
| 3 |
Correct |
1 ms |
364 KB |
Output is correct |
| 4 |
Correct |
259 ms |
17032 KB |
Output is correct |
| 5 |
Correct |
263 ms |
13036 KB |
Output is correct |
| 6 |
Correct |
254 ms |
17388 KB |
Output is correct |
| 7 |
Correct |
1 ms |
364 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
267 ms |
12884 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
364 KB |
Output is correct |
| 2 |
Correct |
1 ms |
364 KB |
Output is correct |
| 3 |
Incorrect |
1 ms |
364 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
