Submission #771247

#	Time	Username	Problem	Language	Result	Execution time	Memory
771247		siewjh	Bridges (APIO19_bridges)	C++17	100 / 100	2976 ms	9180 KiB

bridges

#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
const int MAXN = 50005;
int par[MAXN], sz[MAXN];
vector<pair<int, int>> jst;
int root(int x){
	if (par[x] == -1) return x;
	else return root(par[x]);
}
void join(int a, int b){
	int ra = root(a), rb = root(b);
	if (ra == rb) return;
	if (sz[ra] < sz[rb]) swap(ra, rb); // ra larger
	par[rb] = ra;
	sz[ra] += sz[rb];
	jst.push_back({ra, rb});
}
void rollback(){
	while (!jst.empty()){
		int ra, rb; tie(ra, rb) = jst.back(); jst.pop_back();
		par[rb] = -1;
		sz[ra] -= sz[rb];
	}
}
int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(0); cout.tie(0);
	int nodes, edges; cin >> nodes >> edges;
	vector<int> ea(edges + 1), eb(edges + 1), ew(edges + 1);
	for (int i = 1; i <= edges; i++){
		int a, b, w; cin >> a >> b >> w;
		ea[i] = a; eb[i] = b; ew[i] = w;
	}
	int queries; cin >> queries;
	vector<int> qt(queries), qx(queries), qw(queries);
	for (int i = 0; i < queries; i++){
		int typ, ind, w; cin >> typ >> ind >> w;
		qt[i] = typ; qx[i] = ind; qw[i] = w;
	}
	vector<int> ans(queries, -1);
	const int bsz = 420;
	vector<int> dyna[bsz];
	for (int l = 0; l < queries; l += bsz){
		int r = min(l + bsz, queries) - 1;
		for (int i = 1; i <= nodes; i++){
			par[i] = -1;
			sz[i] = 1;
		}
		vector<bool> ch(edges + 1, 0);
		vector<int> qv, stat, chv;
		for (int i = l; i <= r; i++){
			if (qt[i] == 1)
				ch[qx[i]] = 1;
		}
		for (int i = 1; i <= edges; i++){
			if (ch[i]) chv.push_back(i);
			else stat.push_back(i);
		}
		for (int i = l; i <= r; i++){
			int x = qx[i], w = qw[i];
			if (qt[i] == 1) ew[x] = w;
			else{
				qv.push_back(i);
				dyna[i - l].clear();
				for (int eind : chv)
					if (ew[eind] >= w)
						dyna[i - l].push_back(eind);
			}
		}
		sort(stat.begin(), stat.end(), [&](int a, int b){return ew[a] > ew[b];});
		sort(qv.begin(), qv.end(), [&](int a, int b){return qw[a] > qw[b];});
		int stind = 0;
		for (int qind : qv){
			int w = qw[qind], x = qx[qind];
			while (stind != stat.size() && ew[stat[stind]] >= w){
				int eind = stat[stind];
				join(ea[eind], eb[eind]);
				stind++;
			}
			jst.clear();
			for (int eind : dyna[qind - l]) join(ea[eind], eb[eind]);
			ans[qind] = sz[root(x)];
			rollback();
		}
	}
	for (int i = 0; i < queries; i++)
		if (ans[i] != -1)
			cout << ans[i] << '\n';
	return 0;
}

Compilation message (stderr)

bridges.cpp: In function 'int main()':
bridges.cpp:76:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   76 |    while (stind != stat.size() && ew[stat[stind]] >= w){
      |           ~~~~~~^~~~~~~~~~~~~~

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