Submission #1267212

#	Time	Username	Problem	Language	Result	Execution time	Memory
1267212		RiverFlow	Making Friends on Joitter is Fun (JOI20_joitter2)	C++20	100 / 100	904 ms	70808 KiB

joitter2

#include <bits/stdc++.h>

#define nl "\n"
#define no "NO"
#define yes "YES"
#define fi first
#define se second
#define vec vector
#define task "main"
#define _mp make_pair
#define ii pair<int, int>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define evoid(val) return void(std::cout << val)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FOD(i, b, a) for(int i = (b); i >= (a); --i)
#define unq(x) sort(all(x)); x.resize(unique(all(x)) - x.begin())

using namespace std;

template<typename U, typename V> bool maxi(U &a, V b) {
    if (a < b) { a = b; return 1; } return 0;
}
template<typename U, typename V> bool mini(U &a, V b) {
    if (a > b) { a = b; return 1; } return 0;
}

const int N = (int)2e5 + 9;
const int mod = (int)1e9 + 7;

void prepare(); void main_code();

int main() {
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if (fopen(task".inp", "r")) {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    const bool MULTITEST = 0; prepare();
    int num_test = 1; if (MULTITEST) cin >> num_test;
    while (num_test--) { main_code(); }
}

void prepare() {};

long long ans = 0;

int par[N], s[N];

int rt(int x) {
    return x == par[x] ? x : par[x] = rt(par[x]);
}

set<pair<int, int>> in[N], out[N];

queue<pair<int, int>> q;

bool check(int x, int y) {
    x = rt(x), y = rt(y);
    auto it1 = out[x].lower_bound({y, 0});
    auto it2 = out[y].lower_bound({x, 0});
    return (it1 != out[x].end() and it2 != out[y].end()
    and it1->first == y and it2->first == x);
}

void unite(int x, int y) {
    x = rt(x), y = rt(y);
    if (x == y) return ;
    if (sz(in[x]) + sz(out[x]) < sz(in[y]) + sz(out[y]))
        swap(x, y);
    ans -= 1LL * s[x] * (s[x] - 1) + 1LL * s[x] * sz(in[x]);
    ans -= 1LL * s[y] * (s[y] - 1) + 1LL * s[y] * sz(in[y]);

//    cerr << x << ' ' << y << ' ' << ans << nl;

    for(ii v : in[y]) {
        if (v.first == x) {
            continue ;
        }
        out[v.first].erase(_mp(y, v.second));
        out[v.first].insert(_mp(x, v.second));

        in[x].insert(v);
        if (check(x, v.first)) {
            q.push(_mp(x, v.first));
        }
    }

    for(ii v : out[y]) {
        if (v.first == x) {
            in[x].erase(_mp(y, v.second));
            continue ;
        }
        in[v.first].erase(_mp(y, v.second));
        in[v.first].insert(_mp(x, v.second));

        out[x].insert(v);

        if (check(x, v.first)) {
            q.push(_mp(x, v.first));
        }
    }

    par[y] = x, s[x] += s[y];
    ans += 1LL * s[x] * (s[x] - 1) + 1LL * s[x] * sz(in[x]);
    cerr << s[x] << ' ' << sz(in[x]) << nl;
}

void main_code() {
    int n, m; cin >> n >> m;
    for(int i = 1; i <= n; ++i) s[i] = 1, par[i] = i;
    for(int i = 1; i <= m; ++i) {
        int x, y; cin >> x >> y;
        int u=x, v=y;
        x = rt(x), y = rt(y);
        if (x != y) {
//            cerr << "i: " << i << ' ' << x << ' ' << u << nl;
            ans -= 1LL * s[y] * sz(in[y]);
            out[x].insert(_mp(y, u));
            in[y].insert(_mp(x, u));
            ans += 1LL * s[y] * sz(in[y]);
            if (check(x, y)) {
                q.push(_mp(x, y));
            }
            while (!q.empty()) {
                auto c = q.front(); q.pop();
                unite(c.first, c.second);
            }
        }
        cout << ans << nl;
    }
}


/*     Let the river flows naturally     */

Compilation message (stderr)

joitter2.cpp: In function 'int main()':
joitter2.cpp:36:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
joitter2.cpp:37:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 1 / 1
• Subtask 2: 16 / 16
• Subtask 3: 83 / 83