Submission #357874

#	Time	Username	Problem	Language	Result	Execution time	Memory
357874		shivensinha4	Bridges (APIO19_bridges)	C++17	100 / 100	2580 ms	8424 KiB

bridges

/*
 * Divide queries into blocks of sqrt(m).
 * For each block, at max sqrt(m) edges will be changed.
 * For the edges which do not change, maintain a set of nodes 
 */
#include "bits/stdc++.h"
using namespace std;
#define for_(i, s, e) for (int i = s; i < (int) e; i++)
#define for__(i, s, e) for (ll i = s; i < e; i++)
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> ii;
#define endl '\n'

class UFDS {
public:
	vi p, rank, sz; int count = 0;
	
	void build(int n) {
		p.assign(n, 0); rank.assign(n, 0); sz.assign(n, 1);
		for_(i, 0, n) p[i] = i;
		count = n;
	}
	int getParent(int i) {
		return (p[i] == i) ? i : (p[i] = getParent(p[i]));
	}
	void join(int i, int j) {
		int a = getParent(i), b = getParent(j);
		if (a == b) return;
		count -= 1;
		if (rank[a] > rank[b]) {
			p[b] = a;
			sz[a] += sz[b];
		} else {
			p[a] = b;
			if (rank[a] == rank[b]) rank[b] += 1;
			sz[b] += sz[a];
		}
	}
};

const int bs = 1000;

int main() {
#ifdef mlocal
	freopen("test.in", "r", stdin);
#endif
	
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	
	int n, m; cin >> n >> m;
	array<int, 2> edge[m]; // {a, b, w}
	int wt[m];
	for_(i, 0, m) {
		cin >> edge[i][0] >> edge[i][1] >> wt[i];
		edge[i][0] -= 1; edge[i][1] -= 1;
	}
	
	int q; cin >> q;
	array<int, 3> qr[q]; // {for car: {type (2), weight, node}
	for_(i, 0, q) {
		cin >> qr[i][0] >> qr[i][1] >> qr[i][2];
		qr[i][1] -= 1;
		if (qr[i][0] == 2) swap(qr[i][1], qr[i][2]);
	}
	
	bool change[m];
	UFDS ufds;
	vector<array<int, 2>> same;
	int pt = 0;
	vector<vi> adj(n);
	int adjChange[n], lastSeen[n];
	vi changed;
	for_(i, 0, n) lastSeen[i] = -1;
	int currWt[m];
	vector<vector<array<int, 2>>> carQr;
	for_(qq, 0, q) {
		if ((qq % bs) == 0) carQr.push_back({});
		if (qr[qq][0] == 2) carQr[carQr.size()-1].push_back({qr[qq][1], qq});
	}
	
	for_(i, 0, carQr.size()) sort(carQr[i].begin(), carQr[i].end(), greater<>());
	
	int bpt = 0;
	vi fin(q, -1);
	for (auto &b: carQr) {
		int bStart = bpt*bs;
		if (b.size()) {
			pt = 0;
			ufds.build(n); same.clear(); changed.clear(); memset(change, false, sizeof(change));
			for_(i, bStart, min(q, bStart+bs)) if (qr[i][0] == 1) change[qr[i][1]] = true;
			
			for_(i, 0, m) {
				if (!change[i]) same.push_back({wt[i], i});
				else changed.push_back(i);
			}
			sort(same.begin(), same.end(), greater<>());
			
			for (auto &car: b) {
				int qq = car[1];
				while (pt < same.size() and same[pt][0] >= qr[qq][1]) {
					ufds.join(edge[same[pt][1]][0], edge[same[pt][1]][1]);
					pt++;
				}
				
				for (auto &e: changed) currWt[e] = wt[e];
				for_(i, bStart, qq) if (qr[i][0] == 1) currWt[qr[i][1]] = qr[i][2];
				for (auto &e: changed) {
					if (currWt[e] < qr[qq][1]) continue;
					int c1 = ufds.getParent(edge[e][0]), c2 = ufds.getParent(edge[e][1]);
					if (c1 == c2) continue;
					if (adjChange[c1] != qq) {
						adjChange[c1] = qq;
						adj[c1].clear();
					}
					if (adjChange[c2] != qq) {
						adjChange[c2] = qq;
						adj[c2].clear();
					}
					
					adj[c1].push_back(c2); adj[c2].push_back(c1);
				}
				
				int cp = ufds.getParent(qr[qq][2]);
				int ans = ufds.sz[cp];
				queue<int> qu;
				lastSeen[cp] = qq;
				qu.push(cp);
				while (qu.size()) {
					int p = qu.front(); qu.pop();
					if (adjChange[p] == qq) for (auto i: adj[p])  {
							if (lastSeen[i] == qq) continue;
							lastSeen[i] = qq;
							qu.push(i);
							ans += ufds.sz[i];
						}
				}
				fin[qq] = ans;
			}
		}
		
		for_(i, bStart, min((bpt+1)*bs, q)) if (qr[i][0] == 1) wt[qr[i][1]] = qr[i][2];
		bpt++;
	}
	
	for (auto i: fin) if (i != -1) cout << i << endl;
	
	return 0;
}

Compilation message (stderr)

bridges.cpp: In function 'int main()':
bridges.cpp:102:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::array<int, 2> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  102 |     while (pt < same.size() and same[pt][0] >= qr[qq][1]) {
      |            ~~~^~~~~~~~~~~~~

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