제출 #1196201

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1196201		countless	Duathlon (APIO18_duathlon)	C++20	0 / 100	21 ms	6728 KiB

count_triplets

#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];
    }

    if (n <= 2) {
        cout << 0 << endl;
        return;
    }
    
    cout << 2LL * pref[n-2] << 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

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 8
• Subtask 4: 0 / 10
• Subtask 5: 0 / 13
• Subtask 6: 0 / 15
• Subtask 7: 0 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10