This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
//thatsramen
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define eb emplace_back
#define pb push_back
#define ft first
#define sd second
#define pi pair<int, int>
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define dbg(...) dbg_out(__VA_ARGS__)
using ll = long long;
using ld = long double;
using namespace std;
using namespace __gnu_pbds;
//Constants
const ll INF = 5 * 1e18;
const int IINF = 2 * 1e9;
const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;
const ll dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const ld PI = 3.14159265359;
//Templates
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) {return os << '(' << p.first << ", " << p.second << ')';}
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) {os << '['; string sep; for (const T &x : v) os << sep << x, sep = ", "; return os << ']';}
void dbg_out() {cerr << endl;}
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << H << ' '; dbg_out(T...); }
template<typename T> void mins(T& x, T y) {x = min(x, y);}
template<typename T> void maxs(T& x, T y) {x = max(x, y);}
template<typename T> using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T> using omset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
//order_of_key(k): number of elements strictly less than k
//find_by_order(k): k-th element in the set
void setPrec() {cout << fixed << setprecision(15);}
void unsyncIO() {cin.tie(0)->sync_with_stdio(0);}
void setIn(string s) {freopen(s.c_str(), "r", stdin);}
void setOut(string s) {freopen(s.c_str(), "w", stdout);}
void setIO(string s = "") {
unsyncIO(); setPrec();
if(s.size()) setIn(s + ".in"), setOut(s + ".out");
}
// #define TEST_CASES
void solve() {
int n;
cin >> n;
map<string, string> to;
for (int i = 0; i < n; i++) {
string u, v; cin >> u >> v;
to[u] = v;
}
map<string, bool> vis;
int left = 0; int dep = 0;
function<void(string, string)> dfs = [&](string f, string p) {
vis[f] = true; dep++;
string t = to[f];
if (!vis.count(t)) {
dfs(t, f);
} else if (t == p) {
dep -= 2;
}
};
int ans = 0;
for (auto [st, pp] : to) {
if (!vis.count(st)) {
dfs(st, "-1");
ans += dep / 2;
left += dep & 1;
dep = 0;
}
}
if (left & 1) {
cout << "-1";
return;
}
ans += left;
cout << ans;
}
int main() {
setIO();
int tt = 1;
#ifdef TEST_CASES
cin >> tt;
#endif
while (tt--)
solve();
return 0;
}
Compilation message (stderr)
polygon.cpp: In function 'void setIn(std::string)':
polygon.cpp:44:30: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
44 | void setIn(string s) {freopen(s.c_str(), "r", stdin);}
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
polygon.cpp: In function 'void setOut(std::string)':
polygon.cpp:45:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
45 | void setOut(string s) {freopen(s.c_str(), "w", stdout);}
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
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