#include <bits/stdc++.h>
// author: aykhn
using namespace std;
#define int long long
#define inf 0x3F3F3F3F
const int MXN = 1e5 + 5;
int n;
vector<int> adj[MXN], g[MXN];
map<string, int> mp;
string name[MXN];
int to[MXN], dp[MXN][2];
int col[MXN], in[MXN], mark[MXN], p[MXN];
vector<int> id[MXN];
int idx = 0;
int cyc(int a)
{
col[a] = 1;
for (int v : g[a])
{
if (col[v] == 2)
{
continue;
}
if (col[v] == 1)
{
idx++;
int s = a;
int e = v;
while (1)
{
in[s] = 1;
id[idx].push_back(s);
if (s == e) break;
s = p[s];
}
return 1;
}
else
{
p[v] = a;
if (cyc(v))
{
col[a] = 2;
return 1;
}
}
}
col[a] = 2;
return 0;
}
void dfs(int a)
{
if (adj[a].empty())
{
dp[a][0] = dp[a][1] = 1;
return;
}
dp[a][0] = 0;
dp[a][1] = inf;
for (int v : adj[a])
{
dfs(v);
dp[a][0] += min(dp[v][0], dp[v][1]);
}
for (int v : adj[a])
{
dp[a][1] = min(dp[a][1], dp[a][0] - min(dp[v][0], dp[v][1]) + dp[v][0] - 1);
}
dp[a][0]++;
assert(dp[a][0] >= dp[a][1]);
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(nullptr);
int n, m = 0, cnt = 0;
cin >> n;
if (n & 1)
{
cout << -1 << '\n';
return 0;
}
for (int i = 1; i <= n; i++)
{
string a, b;
cin >> a >> b;
if (mp.find(a) == mp.end()) mp[a] = ++m, name[m] = a;
if (mp.find(b) == mp.end()) mp[b] = ++m, name[m] = b;
to[mp[a]] = mp[b];
}
vector<int> r;
int res = 0;
for (int i = 1; i <= m; i++)
{
if (to[to[i]] == i)
{
res--;
mark[i] = 1, mark[to[i]] = 1;
continue;
}
if (to[to[to[i]]] == to[i]) to[i] = i;
g[i].push_back(to[i]);
}
for (int i = 1; i <= m; i++)
{
if (mark[i]) continue;
if (!col[i])
{
p[i] = i;
cyc(i);
}
}
for (int i = 1; i <= m; i++)
{
if (mark[i]) continue;
if (!(in[i] && in[to[i]]))
{
adj[to[i]].push_back(i);
}
}
for (int i = 1; i <= m; i++)
{
if (in[i]) dfs(i);
}
for (int c = 1; c <= idx; c++)
{
if (id[c].size() == 1)
{
res += dp[id[c][0]][1];
continue;
}
int ans = 0, sz = (int)id[c].size(), mn = 0;
for (int x : id[c]) ans += dp[x][1];
vector<array<int, 2>> dpp(id[c].size(), {inf, inf}), dps(id[c].size(), {inf, inf});
dpp[0][1] = dp[id[c][0]][0] - dp[id[c][1]][1];
dpp[0][0] = 0;
for (int i = 1; i < id[c].size(); i++)
{
dpp[i][0] = min(0LL, dpp[i - 1][1] + dp[id[c][i]][0] - dp[id[c][i]][1] - 2);
dpp[i][1] = dpp[i - 1][0] + dp[id[c][i]][0] - dp[id[c][i]][1];
mn = min(mn, dp[i][0]);
}
dps[sz - 1][1] = dp[id[c][sz - 1]][0] - dp[id[c][sz - 1]][1];
for (int i = sz - 1; i >= 0; i--)
{
dps[i][0] = min(0LL, dps[i + 1][1] + dp[id[c][i]][0] - dp[id[c][i]][1] - 2);
dps[i][1] = dps[i + 1][0] + dp[id[c][i]][0] - dp[id[c][i]][1];
}
}
}
Compilation message
polygon.cpp: In function 'int main()':
polygon.cpp:142:27: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
142 | for (int i = 1; i < id[c].size(); i++)
| ~~^~~~~~~~~~~~~~
polygon.cpp:81:19: warning: unused variable 'cnt' [-Wunused-variable]
81 | int n, m = 0, cnt = 0;
| ^~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3 ms |
13912 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3 ms |
13916 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
915 ms |
1048576 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3 ms |
13912 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
