Submission #97143

#	Time	Username	Problem	Language	Result	Execution time	Memory
97143		dndhk	Pipes (CEOI15_pipes)	C++14	100 / 100	1563 ms	8376 KiB

pipes

#include <iostream>
#include <vector>
#include <stdio.h>
#include <algorithm>

#define MAX_N 100000

using namespace std;

int N, M;
pair<int, int> gp[MAX_N*4+1];
int sz = 0;
int g1[MAX_N+1], g2[MAX_N+1];
int up[MAX_N+1], lv[MAX_N+1], p[MAX_N+1];

int find_g1(int x){
	if(x==g1[x])	return x;
	return g1[x] = find_g1(g1[x]);
}

int find_g2(int x){
	if(x==g2[x])	return x;
	return g2[x] = find_g2(g2[x]);
}

int s, e, m;

void dfs(int x){
	bool tf = true;
	up[x] = lv[x];
	s = 0, e = sz-1;
	while(s<e){
		m = (s+e)/2;
		if(gp[m].first<x) s = m+1;
		else	e = m;
	}
	for(int i=s; i<sz; i++){
		if(gp[i].first!=x)	break;
		if(gp[i].second==p[x] && tf){
			tf = false; continue;
		}	
		if(lv[gp[i].second]!=0){
			up[x] = min(up[x], lv[gp[i].second]);
		}else{
			p[gp[i].second] = x;
			lv[gp[i].second] = lv[x]+1;
			dfs(gp[i].second);
			if(up[gp[i].second]>lv[x])	printf("%d %d\n", gp[i].second, x);
			up[x] = min(up[x], up[gp[i].second]);
		}
	}
}

int main(){
	scanf("%d %d", &N, &M);
	for(int i=1; i<=N; i++)	g1[i] = g2[i] = i;
	int a, b;
	while(M--){
		scanf("%d%d", &a, &b);
		if(find_g1(a)!=find_g1(b)){
			gp[sz++] = {a, b}; gp[sz++] = {b, a};
			a = find_g1(a); b = find_g1(b);
			g1[a] = b;
		}
		else if(find_g2(a)!=find_g2(b)){
			gp[sz++] = {a, b}; gp[sz++] = {b, a};
			a = find_g2(a); b = find_g2(b);
			g2[a] = b;
		}
	}sort(gp, gp+sz);
	for(int i=1; i<=N; i++){
		if(lv[i]==0){
			lv[i] = 1;
			dfs(i);
		}
	}
	return 0;
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:55:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &N, &M);
  ~~~~~^~~~~~~~~~~~~~~~~
pipes.cpp:59:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &a, &b);
   ~~~~~^~~~~~~~~~~~~~~~

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