# | Time | Username | Problem | Language | Result | Execution time | Memory |
---|---|---|---|---|---|---|---|
1196204 | countless | 철인 이종 경기 (APIO18_duathlon) | C++20 | 0 ms | 0 KiB |
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
const ll MOD = 998244353;
const ll INF = 1e18;
const ld EPS = 1e-12;
#define endl "\n"
#define sp <<" "<<
#define REP(i, a, b) for(ll i = a; i < b; i++)
#define dbg(x) cout << #x << " = " << x << endl
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define fast_io() ios_base::sync_with_stdio(false); cin.tie(NULL)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) ((ll)(x).size())
struct custom_hash {
static uint64_t splitmix64(uint64_t x) {
// http://xorshift.di.unimi.it/splitmix64.c
x += 0x9e3779b97f4a7c15;
x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
return x ^ (x >> 31);
}
size_t operator()(uint64_t x) const {
static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
return splitmix64(x + FIXED_RANDOM);
}
};
template <typename Key, typename Value>
using hash_map = unordered_map<Key, Value, custom_hash>;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
// uniform_int_distribution<int>(a, b)(rng);
// shuffle(all(a), rng);
void solution() {
int n, m; cin >> n >> m;
vector<vector<int>> adj(n);
REP(i, 0, m) {
int u, v; cin >> u >> v; --u, --v;
adj[u].push_back(v);
adj[v].push_back(u);
}
// subtask 3
vector<ll> pref(n+1);
iota(all(pref), 0);
REP(i, 1, n+1) {
pref[i] += pref[i-1];
}
REP(i, 1, n+1) {
pref[i] += pref[i-1];
}
ll ans = 0;
vector<bool> vis(n);
auto end = [&](this auto &&self, int u, int p = -1) -> ll {
for (auto &v : adj[u]) {
if (v != p) {
return self(v, u);
}
}
return u;
};
auto size = [&](this auto &&self, int u, int p = -1) -> ll {
vis[u] = true;
for (auto &v : adj[u]) {
if (v != p) {
return self(v, u) + 1;
}
}
return 1;
};
auto find = [&](int u) -> ll {
ll st = end(u);
ll ln = size(st);
if (ln <= 2) return 0;
return 2LL * pref[n-2];
};
REP(i, 0, n) {
if (vis[i]) continue;
ans += find(i);
}
cout << ans << endl;
return;
}
signed main() {
fast_io();
solution();
return 0;
}
// Notes
// is it binsearchable?
// is it greedy?
// is it DP?
// if online round: search OEIS, similar topics
// put observations together
// check for edge cases
// try "dumb" solutions, you're fast enough to rewrite
// clean up the implementation
// keep it simple
// check for overflow
// check for small N
// check for array with same or monotonic a_i