#include <iostream>
#include <algorithm>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <iomanip>
#include <cassert>
#include <stack>
#include <queue>
#include <deque>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>-
using namespace std;
//using namespace __gnu_pbds;
typedef long long ll;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
// template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
// order_of_key (k) : Number of items strictly smaller than k .
// find_by_order(k) : K-th element in a set (counting from zero).
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define pb push_back
#define ppb pop_back
#define mkp make_pair
#define F first
#define S second
#define lb lower_bound
#define ub upper_bound
#define show(a) cerr << #a <<" -> "<< a <<" "
#define nl cerr <<"\n"
//#define int ll
const int N = 5005;
const int oo = 1e9 + 5;
int n, d[N][N], mx, ans, cnt[N], cycle[N];
vector <int> g[N];
queue <int> q;
bool was[N], good = 1;
void dfs(int v, int col) {
was[v] = 1;
cycle[v] = col;
for (int to : g[v]) {
if (was[to]) { continue; }
if (!cnt[to]) { dfs(to, col); }
}
}
void solve() {
cin >> n;
for (int i = 1; i <= n; ++i) {
int a, b;
cin >> a >> b;
g[a].pb(b);
g[b].pb(a);
}
for (int i = 1; i <= n; ++i) {
cnt[i] = sz(g[i]);
if (sz(g[i]) == 1) { q.push(i); }
}
while(sz(q)) {
int v = q.front(); q.pop();
--cnt[v];
for (int to : g[v]) {
if (cnt[to] > 1) { --cnt[to]; }
if (cnt[to] == 1) { q.push(to); }
}
}
int len = 0;
for (int i = 1; i <= n; ++i) {
if (cnt[i]) { ++len; } assert(cnt[i] == 0 || cnt[i] == 2);
}
for (int i = 1; i <= n; ++i) {
if (cycle[i]) { continue; }
if (cnt[i] == 2) {
dfs(i, i);
}
}
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= n; ++j) { d[i][j] = oo; }
d[i][i] = 0;
q.push(i);
while (sz(q)) {
int v = q.front();
q.pop();
for (int to : g[v]) {
if (d[i][to] > d[i][v] + 1) {
d[i][to] = d[i][v] + 1;
q.push(to);
}
}
}
for (int j = 1; j <= n; ++j) { mx = max(mx, d[i][j]); }
}
for (int i = 1; i < n; ++i) {
for (int j = i+1; j <= n; ++j) {
if (mx == d[i][j]) {
++ans;
if (d[ cycle[i] ][ cycle[j] ] != len / 2) { good = 0; }
}
}
}
if (len % 2 == 0 && good) ans *= 2;
cout << ans;
}
main () {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int tests = 1;
//cin >> tests;
while (tests --) {
solve();
}
return 0;
}
/*
Just Chalish!
7
1 4
2 4
3 4
4 5
5 6
6 7
5 7
8
1 2
1 3
4 3
4 2
3 5
5 6
4 7
7 8
*/
Compilation message
shymbulak.cpp:114:8: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
114 | main () {
| ^
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
620 KB |
Output is correct |
| 2 |
Correct |
1 ms |
492 KB |
Output is correct |
| 3 |
Correct |
1 ms |
492 KB |
Output is correct |
| 4 |
Correct |
1 ms |
492 KB |
Output is correct |
| 5 |
Correct |
1 ms |
492 KB |
Output is correct |
| 6 |
Incorrect |
1 ms |
620 KB |
Output isn't correct |
| 7 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
19 ms |
5228 KB |
Output is correct |
| 2 |
Correct |
16 ms |
6252 KB |
Output is correct |
| 3 |
Correct |
24 ms |
8428 KB |
Output is correct |
| 4 |
Incorrect |
24 ms |
8428 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
58 ms |
11500 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
| 2 |
Halted |
0 ms |
0 KB |
- |
