oj.uz

Submission #527379

# Submission time Handle Problem Language Result Execution time Memory
527379 2022-02-17T10:01:11 Z jamielim Pipes (CEOI15_pipes) C++14
100 / 100
 1398 ms 14200 KB 
#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define mp make_pair
#define pb emplace_back
#define ALL(x) x.begin(),x.end()
#define SZ(x) (int)x.size()
typedef long long ll;
typedef pair<int,int> ii;
typedef pair<ii,ii> i4;
const int MOD=1000000007;
const int INF=1012345678;
const ll LLINF=1012345678012345678LL;
const double PI=3.1415926536;
const double EPS=1e-14;

const int MAXN=100005;
int n,m;
int par[MAXN],par2[MAXN]; // par, depth
int root(int x){return par[x]=(par[x]==x?x:root(par[x]));}
int root2(int x){return par2[x]=(par2[x]==x?x:root2(par2[x]));}
vector<int> adj[MAXN]; // only stores at most 2*tree

int low[MAXN];
int ctr=0;
void dfs(int x){
	par2[x]=low[x]=ctr++;
	bool p=0;
	for(int i:adj[x]){
		if(i==par[x]&&!p){
			p=1;
			continue;
		}
		if(par2[i]==-1){
			par[i]=x;
			dfs(i);
			low[x]=min(low[x],low[i]);
			if(low[i]>par2[x])printf("%d %d\n",i+1,x+1);
		}else low[x]=min(low[x],par2[i]);
	}
}

int main(){
	scanf("%d%d",&n,&m);
	for(int i=0;i<n;i++)par[i]=par2[i]=i;
	int a,b;
	for(int i=0;i<m;i++){
		scanf("%d%d",&a,&b);a--;b--;
		//if a,b are in different trees, merge the two trees
		int ra=root(a),rb=root(b);
		if(ra!=rb){
			par[ra]=rb;
			adj[a].pb(b);
			adj[b].pb(a);
			continue;
		}
		//otherwise, take note that later we have to get rid of the entire cycle
		int r2a=root2(a),r2b=root2(b);
		if(r2a!=r2b){
			par2[r2a]=par2[r2b];
			adj[a].pb(b);
			adj[b].pb(a);
		}
	}
	memset(par,-1,sizeof(par));
	memset(par2,-1,sizeof(par2));
	memset(low,-1,sizeof(low));
	for(int i=0;i<n;i++)if(par2[i]==-1)dfs(i);
}

Compilation message

pipes.cpp: In function 'int main()':
pipes.cpp:46:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   46 |  scanf("%d%d",&n,&m);
      |  ~~~~~^~~~~~~~~~~~~~
pipes.cpp:50:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |   scanf("%d%d",&a,&b);a--;b--;
      |   ~~~~~^~~~~~~~~~~~~~

Subtask #1
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 3788 KB Output is correct
2 Correct 2 ms 3788 KB Output is correct

Subtask #2
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 4172 KB Output is correct
2 Correct 6 ms 3916 KB Output is correct

Subtask #3
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 110 ms 4096 KB Output is correct
2 Correct 114 ms 3908 KB Output is correct

Subtask #4
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 250 ms 4768 KB Output is correct
2 Correct 226 ms 4248 KB Output is correct

Subtask #5
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 316 ms 6076 KB Output is correct
2 Correct 293 ms 5624 KB Output is correct

Subtask #6
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 420 ms 10612 KB Output is correct
2 Correct 407 ms 7276 KB Output is correct

Subtask #7
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 707 ms 11604 KB Output is correct
2 Correct 620 ms 8756 KB Output is correct

Subtask #8
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 988 ms 13588 KB Output is correct
2 Correct 858 ms 8580 KB Output is correct

Subtask #9
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 1096 ms 13564 KB Output is correct
2 Correct 1115 ms 10824 KB Output is correct

Subtask #10
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 1398 ms 13056 KB Output is correct
2 Correct 1334 ms 14200 KB Output is correct