#include <bits/stdc++.h>
#define ff first
#define ss second
#define mp make_pair
#define fast_io do { ios::sync_with_stdio(false), cin.tie(0); } while(0)
#ifdef TDEBUG
#define debug(...) dout(#__VA_ARGS__, __VA_ARGS__)
#define cdeb cout
#define dfast_io do {} while(0)
#else
#define debug(...) do {} while(0)
struct dostream {} cdeb;
#define dfast_io fast_io
template<typename T>
dostream& operator<<(dostream& out, T&& t) { return out; }
#endif
template<typename T>
void dout(std::string const& name, T arg) { std::cerr << name << " = " << arg << std::endl; }
template<typename T1, typename... T2>
void dout(std::string const& names, T1 arg, T2... args) {
std::cerr << names.substr(0, names.find(',')) << " = " << arg << " | ";
dout(names.substr(names.find(',') + 2), args...);
}
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
template<typename A, typename B>
ostream& operator<<(ostream& out, pair<A, B> const& p) { out << "(" << p.ff << ", " << p.ss << ")"; return out; }
template<typename T>
ostream& operator<<(ostream& out, vector<T> const& v) { for (auto const& e : v) out << e << " "; return out; }
template<typename T>
ostream& operator<<(ostream& out, pair<T*,int> p) { for (;p.ss--;p.ff++) out << *p.ff << " "; return out; }
const int maxn = 1e5 + 10;
const int inf = 0x3f3f3f3f;
const int mod = 1e9 + 7;
vector<int> grafo[maxn], ciclo;
int n, pai[maxn], ch[maxn];
bool mark[maxn], mark2[maxn], in_cycle[maxn];
int dp2[maxn][2][2], dp[maxn][2][2][2][2];
int find_cycle(int u, int p = 0) {
mark[u] = true;
mark2[u] = true;
int ret = 0;
for (auto v : grafo[u]) {
if (v == p) continue;
if (mark2[v]) {
in_cycle[u] = true;
ciclo.push_back(u);
return v;
} else if (!mark[v]) {
int x = find_cycle(v, u);
if (x) {
if (x == -1)
return -1;
in_cycle[u] = true;
ciclo.push_back(u);
return (x == u ? -1 : x);
}
}
}
return 0;
}
void dfs(int u) {
for (auto v : grafo[u]) {
if (v == pai[u] || in_cycle[v]) continue;
pai[v] = u;
ch[u]++;
dfs(v);
}
}
int solve_tree(int u, bool c, bool pc) {
if (ch[u] == 0)
return pc ? c : inf;
if (dp2[u][c][pc] != -1)
return dp2[u][c][pc];
int sum = 0;
vector<pii> s;
s.reserve(ch[u]);
for (auto v : grafo[u]) {
if (v == pai[u] || in_cycle[v]) continue;
s.push_back({v, solve_tree(v, 0, c)});
sum += s.back().ss;
}
int& ans = dp2[u][c][pc];
ans = inf;
if (pc) {
ans = sum;
} else {
for (auto [v, d] : s) {
ans = min(ans, sum - d + solve_tree(v, 1, c));
}
}
ans += c;
return ans;
}
int solve(int i, bool c, bool pc, bool choose_1, bool should_n) {
int u = ciclo[i];
int& ans = dp[i][c][pc][choose_1][should_n];
if (ans != -1)
return ans;
if (i == (int)ciclo.size() - 1) {
if (should_n != c || choose_1 && pc)
return ans = inf;
return ans = solve_tree(u, c, (choose_1 || pc));
}
if (pc) {
ans = solve_tree(u, c, 1) + solve(i+1, 0, c, choose_1, i==0?0:should_n);
} else {
ans = solve_tree(u, c, 0) + solve(i+1, 0, c, choose_1, i==0?0:should_n);
ans = min(ans, solve_tree(u, c, 1) + solve(i+1, 1, c, choose_1, i==0?0:should_n));
if (i == 0) {
ans = min(ans, solve_tree(u, c, 1) + solve(i+1, 0, c, choose_1, i==0?1:should_n));
}
}
ans = min(ans, inf);
return ans;
}
int main() {
memset(dp, -1, sizeof dp);
memset(dp2, -1, sizeof dp2);
dfast_io;
cin >> n;
for (int i = 1; i <= n; i++) {
int a, b;
cin >> a >> b;
grafo[a].push_back(b);
grafo[b].push_back(a);
}
find_cycle(1);
for (auto u : ciclo)
dfs(u);
int ans = min(solve(0, 1, 0, 1, 0), solve(0, 0, 0, 0, 0));
cout << (ans >= inf ? -1 : ans) << '\n';
// cin >> n;
// for (int i = 1; i < n; i++) {
// int a, b;
// cin >> a >> b;
// grafo[a].push_back(b);
// grafo[b].push_back(a);
// }
// dfs(1);
// cout << solve_tree(1, 0, 0) << '\n';
// cout << solve_tree(1, 1, 0) << '\n';
return 0;
}
Compilation message
Main.cpp: In function 'int find_cycle(int, int)':
Main.cpp:49:9: warning: unused variable 'ret' [-Wunused-variable]
49 | int ret = 0;
| ^~~
Main.cpp: In function 'int solve(int, bool, bool, bool, bool)':
Main.cpp:118:39: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
118 | if (should_n != c || choose_1 && pc)
| ~~~~~~~~~^~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
10452 KB |
Output is correct |
| 2 |
Correct |
5 ms |
10452 KB |
Output is correct |
| 3 |
Correct |
5 ms |
10452 KB |
Output is correct |
| 4 |
Correct |
5 ms |
10504 KB |
Output is correct |
| 5 |
Correct |
100 ms |
28024 KB |
Output is correct |
| 6 |
Correct |
107 ms |
28140 KB |
Output is correct |
| 7 |
Correct |
111 ms |
28056 KB |
Output is correct |
| 8 |
Correct |
106 ms |
28072 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
5 ms |
10452 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
5 ms |
10452 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
10452 KB |
Output is correct |
| 2 |
Correct |
5 ms |
10452 KB |
Output is correct |
| 3 |
Correct |
5 ms |
10452 KB |
Output is correct |
| 4 |
Correct |
5 ms |
10504 KB |
Output is correct |
| 5 |
Correct |
100 ms |
28024 KB |
Output is correct |
| 6 |
Correct |
107 ms |
28140 KB |
Output is correct |
| 7 |
Correct |
111 ms |
28056 KB |
Output is correct |
| 8 |
Correct |
106 ms |
28072 KB |
Output is correct |
| 9 |
Incorrect |
5 ms |
10452 KB |
Output isn't correct |
| 10 |
Halted |
0 ms |
0 KB |
- |
