Submission #1034727

#	Time	Username	Problem	Language	Result	Execution time	Memory
1034727		vjudge1	Pipes (CEOI15_pipes)	C++17	40 / 100	686 ms	65536 KiB

pipes

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

const int N = 100'010;
struct dsu {
	int e[N];
	int find(int x) { return e[x] < 0 ? x : e[x] = find(e[x]); }
	bool join(int a, int b) {
		a = find(a), b = find(b);
		if (a == b) return false;
		if (e[a] > e[b]) swap(a, b);
		e[a] += e[b]; e[b] = a;
		return true;
	}
} d1, d2;
vector<int> g[N];
int timer=0;
void dfs(int &at, int &par) {
	bool ck=0;
	d1.e[at]=d2.e[at]=++timer;
	for(int &to:g[at]) {
		if(to == par and ck==0) {
			ck=1;
			continue;
		}
		if(d2.e[to]) {
			d1.e[at]=min(d1.e[at], d2.e[to]);		
		} else {
			dfs(to, at);
			d1.e[at]=min(d1.e[at], d1.e[to]);
		}
	}
	if(d1.e[at] == d2.e[at] and at!=par) {
		cout << at << " " << par << "\n";
	}
}
int main() {
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(cin.failbit);
	int n, m;
	cin >> n >> m;
	int u, v;
	for(int i = 1;i<N;i++)d1.e[i]=d2.e[i]=-1;
	for(int i = 0;i<m;i++) {
		cin >> u >> v;
		if(d1.join(u, v) || d2.join(u, v)) {
			g[u].push_back(v);
			g[v].push_back(u);
		}
	}
	for(int i = 1;i<=N;i++)d1.e[i]=d2.e[i]=0;
	for(int i= 1;i<=n;i++) {
		if(!d1.e[i]) {
			dfs(i, i);
		}
	}
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:51:40: warning: iteration 100009 invokes undefined behavior [-Waggressive-loop-optimizations]
   51 |  for(int i = 1;i<=N;i++)d1.e[i]=d2.e[i]=0;
      |                                 ~~~~~~~^~
pipes.cpp:51:17: note: within this loop
   51 |  for(int i = 1;i<=N;i++)d1.e[i]=d2.e[i]=0;
      |                ~^~~
pipes.cpp:51:40: warning: 'void* __builtin_memset(void*, int, long unsigned int)' forming offset [400040, 400043] is out of the bounds [0, 400040] of object 'd2' with type 'dsu' [-Warray-bounds]
   51 |  for(int i = 1;i<=N;i++)d1.e[i]=d2.e[i]=0;
      |                                 ~~~~~~~^~
pipes.cpp:15:7: note: 'd2' declared here
   15 | } d1, d2;
      |       ^~
pipes.cpp:51:32: warning: 'void* __builtin_memset(void*, int, long unsigned int)' forming offset [400040, 400043] is out of the bounds [0, 400040] of object 'd1' with type 'dsu' [-Warray-bounds]
   51 |  for(int i = 1;i<=N;i++)d1.e[i]=d2.e[i]=0;
      |                         ~~~~~~~^~~~~~~~~~
pipes.cpp:15:3: note: 'd1' declared here
   15 | } d1, d2;
      |   ^~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10