Submission #934415

#	Time	Username	Problem	Language	Result	Execution time	Memory
934415		VladaMG98	Bridges (APIO19_bridges)	C++17	29 / 100	389 ms	24092 KiB

bridges

// Problem: B - Bridges
// Contest: Virtual Judge - 2024-02-27 APIO Simulation
// URL: https://vjudge.net/contest/612540#problem/B
// Memory Limit: 512 MB
// Time Limit: 3000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#include <bits/stdc++.h>
using namespace std;

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define print(A,t) cerr << #A << ": "; copy(all(A),ostream_iterator<t>(cerr," " )); cerr << endl
#define prArr(A,n,t)  cerr << #A << ": "; copy(A,A + n,ostream_iterator<t>(cerr," " )); cerr << endl
#define what_is(x) cerr << #x << " is " << x << endl
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef vector<int> vi;

const int MAXN = 100010;
int from[MAXN], to[MAXN], weg[MAXN];
int type[MAXN], a[MAXN], b[MAXN];
vector<int> g[MAXN];

void dfs (int src, int bnd, vector<bool> &visited) {
    visited[src] = true;
    for (int e : g[src]) {
        int ot = from[e] + to[e] - src;
        if (!visited[ot] && bnd <= weg[e]) {
            dfs(ot, bnd, visited);
        }
    }
}

int n, m, q;

void subtask1() {
    for (int qq = 1; qq <= q; qq++) {
        int t = type[qq];
        if (t == 1) {
            weg[a[qq]] = b[qq];
        } else {
            int src = a[qq], boundary = b[qq];
            vector<bool> visited(n + 1, false);
            dfs(src, boundary, visited);
            int ans = 0;
            for (int i = 1; i <= n; i++) {
                if (visited[i]) ans += 1;
            }
            cout << ans << endl;
        }
    }
}

int t[MAXN << 1]; int seg_n;
void build() {
    for (int i = seg_n - 1; i > 0; --i) t[i] = min(t[i << 1], t[i << 1 | 1]);
}
void modify (int pos, int val) {
    for (t[pos += seg_n] = val; pos > 1; pos >>= 1) t[pos >> 1] = min(t[pos], t[pos ^ 1]);
}
int query (int l, int r) {
    int ans = INT_MAX;
    for (l += seg_n, r += seg_n; l < r; l >>= 1, r >>= 1) {
        if (l & 1) ans = min(ans, t[l++]);
        if (r & 1) ans = min(ans, t[--r]);
    }
    return ans;
}
void subtask2() {
    seg_n = n - 1;
    for (int i = 1; i <= m; i++) {
        t[i - 1 + seg_n] = weg[i];
    }
    build();
    for (int qq = 1; qq <= q; qq++) {
        if (type[qq] == 1) {
            int pos = a[qq] - 1, val = b[qq];
            modify(pos, val);
        } else {
            int pos = a[qq] - 1, with = b[qq];
            int can_l = 0, can_r = 0;
            {
                int lo = 0, hi = pos;
                while (lo <= hi) {
                    int mid = (lo + hi) / 2;
                    if (query(pos - mid, pos) < with) {
                        hi = mid - 1;
                    } else {
                        can_l = mid;
                        lo = mid + 1;
                    }
                }
            }
            {
                int lo = 0, hi = n - 1 - pos;
                while (lo <= hi) {
                    int mid = (lo + hi) / 2;
                    if (query(pos, pos + mid) < with) {
                        hi = mid - 1;
                    } else {
                        can_r = mid;
                        lo = mid + 1;
                    }
                }
            }

            cout << can_l + 1 + can_r << endl;
        }
    }
}

struct event {
    int weg; int type;
    // weg --  weight of the edge
    // type -- if positive, an edge
    //         if negative, a query
    event (int _weg, int _type) : weg(_weg), type(_type) {}
    bool operator < (const event &other) const {
        if (weg == other.weg) return type < other.type;
        return weg < other.weg;
    }
};

struct dsu {
    vi par, sz;
    dsu (int _n) {
        par.resize(_n + 1);
        sz.resize(_n + 1);
        for (int i = 1; i <= _n; i++) {
            par[i] = i;
            sz[i] = 1;
        }
    }
    int get (int x) { if (par[x] == x) return x; return par[x] = get(par[x]); }
    bool unite (int u, int v) {
        u = get(u);
        v = get(v);
        if (u == v) return false;
        if (sz[u] > sz[v]) swap(u, v);
        par[u] = v;
        sz[v] += sz[u];
    }
    int get_size (int u) {
        return sz[get(u)];
    }
};
void subtask4() {
    vector<event> events;
    for (int i = 1; i <= m; i++) {
        events.emplace_back(weg[i], i);
    }
    for (int i = 1; i <= q; i++) {
        events.emplace_back(b[i], -i);
    }
    vector<int> answer(q + 1, 0);
    sort(all(events));
    reverse(all(events));
    dsu d(n + 1);
    for (auto e : events) {
        if (e.type > 0) d.unite(from[e.type], to[e.type]);
        else {
            answer[-e.type] = d.get_size(a[-e.type]);
        }
    }
    for (auto anss : answer) {
        cout << anss << endl;
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);

    cin >> n >> m;
    for (int i = 1; i <= m; i++) {
        cin >> from[i] >> to[i] >> weg[i];
        g[from[i]].push_back(i);
        g[to[i]].push_back(i);
    }

    cin >> q;
    for (int i = 1; i <= q; i++) {
        cin >> type[i] >> a[i] >> b[i];
    }

    if (n <= 1000 && m <= 1000 && q <= 10000) {
        subtask1(); return 0;
    }

    bool is_two = false;
    if (m == n - 1) {
        is_two = true;
        for (int i = 1; i <= m; i++) {
            if (from[i] == i && to[i] == i + 1) continue;
            is_two = false;
            break;
        }
    }

    if (is_two) {
        subtask2(); return 0;
    }

    bool is_four = true;
    for (int i = 1; i <= q; i++) {
        if (type[i] != 2) {
            is_four = false;
            break;
        }
    }

    if (is_four) {
        subtask4(); return 0;
    }


    return 0;
}

Compilation message (stderr)

bridges.cpp: In member function 'bool dsu::unite(int, int)':
bridges.cpp:145:15: warning: control reaches end of non-void function [-Wreturn-type]
  145 |         sz[v] += sz[u];

• Subtask 1: 13 / 13
• Subtask 2: 16 / 16
• Subtask 3: 0 / 17
• Subtask 4: 0 / 14
• Subtask 5: 0 / 13
• Subtask 6: 0 / 27