Submission #96859

#	Time	Username	Problem	Language	Result	Execution time	Memory
96859		Retro3014	Pipes (CEOI15_pipes)	C++17	50 / 100	1024 ms	4728 KiB

pipes

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

using namespace std;
#define MAX_N 30000
#define LN 17
typedef long long ll;
typedef pair<int, int> pii;

int N, M;
vector<pii > gp[MAX_N+1];
int num[MAX_N+1];
int p[MAX_N+1][LN];
int up[MAX_N+1];
int lv[MAX_N+1];
bool vst[MAX_N+1];


int find_g(int x){
	for(int i=LN-1; i>=0; i--){
		if(p[x][i]!=0){
			x = p[x][i];
		}
	}
	return x;
}

pii edge[MAX_N+1];
bool chk[MAX_N+1];
int sz = 0;

int lca(int x, int y){
	for(int i=LN-1; i>=0; i--){
		//cout<<i<<' '<<x<<' '<<y<<endl;
		if(lv[p[x][i]]>=lv[y]){
			x = p[x][i];
		}
		if(lv[p[y][i]]>=lv[x]){
			y = p[y][i];
		}
	}
	for(int i=LN-1; i>=0; i--){
		if(p[x][i]!=p[y][i]){
			x = p[x][i]; y = p[y][i];
		}
	}
	if(x!=y)	x = p[x][0];
	return x;
}

void dfs(int x){
	for(int i=0; i<gp[x].size(); i++){
		if(gp[x][i].first==p[x][0])	continue;
		dfs(gp[x][i].first);
		if(up[gp[x][i].first]<=lv[x])	chk[gp[x][i].second] = false;
		up[x] = min(up[x], up[gp[x][i].first]);
	}
}

void init_graph(int x){
	up[x] = lv[x];
	for(int i=1; i<LN; i++)	p[x][i] = p[p[x][i-1]][i-1];
	for(int i=0; i<gp[x].size(); i++){
		if(gp[x][i].first==p[x][0])	continue;
		lv[gp[x][i].first] = lv[x]+1;
		p[gp[x][i].first][0] = x;
		init_graph(gp[x][i].first);
	}
}



int main(){
	scanf("%d%d", &N, &M);
	for(int i=1; i<=N; i++)	num[i] = 1;
	int a, b, k, tmp, t;
	int A, B;
	for(int i=1; i<=N; i++){
		lv[i] = up[i] = 1;
	}
	while(M--){
		scanf("%d%d", &a, &b);
		A = find_g(a); B = find_g(b);
		if(A==B){
			//cout<<'*'<<a<<' '<<b<<endl;
			k = lca(a, b);
			//cout<<k<<endl;
			up[a] = min(up[a], lv[k]);
			up[b] = min(up[b], lv[k]);
		}else{
			if(num[A]>=num[B]){
				tmp = a; a = b; b = tmp;
				tmp = A; A = B; B = tmp;
			}
			t = num[A];
			dfs(A);
			for(int i=1; i<LN; i++){
				p[a][i] = 0;
			}p[a][0] = b;
			lv[a] = lv[b]+1;
			//printf("%d %d\n", a, b);
			gp[a].push_back({b, sz});
			gp[b].push_back({a, sz});
			init_graph(a);
			edge[sz] = {a, b};
			chk[sz] = true;
			sz++;
			num[B] += t;
		}
	}
	for(int i=1; i<=N; i++){
		int k = find_g(i);
		if(!vst[k]){
			vst[k] = true;
			dfs(k);
		}
	}
	for(int i=0; i<sz; i++){
		if(chk[i]){
			printf("%d %d\n", edge[i].first, edge[i].second);
		}
	}
	return 0;
}

Compilation message (stderr)

pipes.cpp: In function 'void dfs(int)':
pipes.cpp:54:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<gp[x].size(); i++){
               ~^~~~~~~~~~~~~
pipes.cpp: In function 'void init_graph(int)':
pipes.cpp:65:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<gp[x].size(); i++){
               ~^~~~~~~~~~~~~
pipes.cpp: In function 'int main()':
pipes.cpp:76:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &N, &M);
  ~~~~~^~~~~~~~~~~~~~~~
pipes.cpp:84:8: 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: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10