oj.uz

Submission #222635

# Submission time Handle Problem Language Result Execution time Memory
222635 2020-04-13T13:11:35 Z jamielim One-Way Streets (CEOI17_oneway) C++14
100 / 100
 491 ms 31080 KB 
#include <bits/stdc++.h>
using namespace std;
 
const int MAXN=100005;
int n,m;
pair<int,int> edge[MAXN];
vector<pair<int,int> > adj[MAXN];

int par[MAXN];
int dep[MAXN];
int low[MAXN];
bool vis[MAXN];
bool bri[MAXN];
int ctr=0;
void dfs(int x){
	vis[x]=1;
	dep[x]=low[x]=ctr++;
	for(int i=0;i<(int)adj[x].size();i++){
		int y=adj[x][i].first;
		if(!vis[y]){ //not yet visited
			par[y]=x;
			dfs(y);
			if(low[y]>dep[x])bri[adj[x][i].second]=1;
			low[x]=min(low[x],low[y]);
		}else if(y!=par[x])low[x]=min(low[x],dep[y]); //visited and is not parent
	}
}
 
int scc[MAXN];
int c=0;
void comp(int x){
	scc[x]=c;
	for(int i=0;i<(int)adj[x].size();i++){
		if(!bri[adj[x][i].second]&&scc[adj[x][i].first]==-1)comp(adj[x][i].first);
	}
}

vector<pair<int,int> > adj2[MAXN];

pair<int,int> q[MAXN];
vector<pair<int,int> > r;
int pa[MAXN][19],idx[MAXN];
int ldep[MAXN];
void dfs2(int x){
	vis[x]=1;
	for(int i=0;i<(int)(adj2[x].size());i++){
		int y=adj2[x][i].first;
		if(!vis[y]){
			pa[y][0]=x;idx[y]=adj2[x][i].second;
			ldep[y]=ldep[x]+1;
			dfs2(y);
		}
	}
}
int lca(int x,int y){
    if(x==y)return x;
    if(ldep[x]<ldep[y])swap(x,y);
    for(int i=18;i>=0;i--){
        if(pa[x][i]!=-1&&ldep[pa[x][i]]>=ldep[y])x=pa[x][i];
    }
    if(x==y)return x;
    for(int i=18;i>=0;i--){
        if(pa[x][i]!=pa[y][i]){x=pa[x][i];y=pa[y][i];}
    }
    return pa[x][0];
}
 
int ans[MAXN]; //0 B, 1 R, -1 L
void dir(int x,int y,int d){
	if(x==y)return;
	if(ans[idx[x]]!=0)return;
	int a=edge[idx[x]].first,b=edge[idx[x]].second;
	if(x==scc[a]){
		ans[idx[x]]=d;dir(scc[b],y,d);
	}else{
		ans[idx[x]]=-d;dir(scc[a],y,d);
	}
}
 
int main(){
	scanf("%d%d",&n,&m);
	memset(par,-1,sizeof(par));memset(dep,-1,sizeof(dep));memset(low,-1,sizeof(low));
	memset(scc,-1,sizeof(scc));
	memset(pa,-1,sizeof(pa));memset(idx,-1,sizeof(idx));memset(ldep,-1,sizeof(ldep));
	int a,b;
	for(int i=0;i<m;i++){
		scanf("%d%d",&a,&b);a--;b--;edge[i]=make_pair(a,b);
		adj[a].push_back(make_pair(b,i));adj[b].push_back(make_pair(a,i));
	}
	for(int i=0;i<n;i++)if(!vis[i])dfs(i);
	//for(int i=0;i<m;i++)if(bri[i])printf("1 ");else printf("0 ");printf("\n");
	for(int i=0;i<n;i++)if(scc[i]==-1){comp(i);c++;}
	for(int i=0;i<m;i++){
		if(bri[i]){
			a=edge[i].first,b=edge[i].second;
			adj2[scc[a]].push_back(make_pair(scc[b],i));adj2[scc[b]].push_back(make_pair(scc[a],i));
		}
	}
	//for(int i=0;i<n;i++)printf("%d ",scc[i]);printf("\n");
	for(int i=0;i<c;i++)vis[i]=0; for(int i=0;i<c;i++)if(!vis[i]){ldep[i]=0;dfs2(i);}
	for(int i=1;i<18;i++)for(int j=0;j<c;j++)if(pa[j][i-1]!=-1)pa[j][i]=pa[pa[j][i-1]][i-1];
	int p;scanf("%d",&p);
	for(int i=0;i<p;i++){
		scanf("%d%d",&q[i].first,&q[i].second);q[i].first--;q[i].second--;
		if(scc[q[i].first]==scc[q[i].second])continue;
		r.push_back(make_pair(ldep[lca(scc[q[i].first],scc[q[i].second])],i));
	}
	sort(r.begin(),r.end());
	for(int i=0;i<(int)r.size();i++){
		a=q[r[i].second].first,b=q[r[i].second].second;
		//printf("%d->%d->%d\n",a,r[i].first,b);
		int l=lca(scc[a],scc[b]);
		dir(scc[a],l,1);
		dir(scc[b],l,-1);
	}
	for(int i=0;i<m;i++){
		if(ans[i]==0)printf("B");
		else if(ans[i]==1)printf("R");
		else printf("L");
	}
}

Compilation message

oneway.cpp: In function 'int main()':
oneway.cpp:100:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for(int i=0;i<c;i++)vis[i]=0; for(int i=0;i<c;i++)if(!vis[i]){ldep[i]=0;dfs2(i);}
  ^~~
oneway.cpp:100:32: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
  for(int i=0;i<c;i++)vis[i]=0; for(int i=0;i<c;i++)if(!vis[i]){ldep[i]=0;dfs2(i);}
                                ^~~
oneway.cpp:81:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&n,&m);
  ~~~~~^~~~~~~~~~~~~~
oneway.cpp:87:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&a,&b);a--;b--;edge[i]=make_pair(a,b);
   ~~~~~^~~~~~~~~~~~~~
oneway.cpp:102:13: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int p;scanf("%d",&p);
        ~~~~~^~~~~~~~~
oneway.cpp:104:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&q[i].first,&q[i].second);q[i].first--;q[i].second--;
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 14 ms 14824 KB Output is correct
2 Correct 17 ms 14848 KB Output is correct
3 Correct 15 ms 14848 KB Output is correct
4 Correct 14 ms 14976 KB Output is correct
5 Correct 14 ms 14976 KB Output is correct
6 Correct 17 ms 14848 KB Output is correct
7 Correct 15 ms 14880 KB Output is correct
8 Correct 18 ms 14976 KB Output is correct
9 Correct 14 ms 14848 KB Output is correct
10 Correct 13 ms 14848 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 14 ms 14824 KB Output is correct
2 Correct 17 ms 14848 KB Output is correct
3 Correct 15 ms 14848 KB Output is correct
4 Correct 14 ms 14976 KB Output is correct
5 Correct 14 ms 14976 KB Output is correct
6 Correct 17 ms 14848 KB Output is correct
7 Correct 15 ms 14880 KB Output is correct
8 Correct 18 ms 14976 KB Output is correct
9 Correct 14 ms 14848 KB Output is correct
10 Correct 13 ms 14848 KB Output is correct
11 Correct 82 ms 20548 KB Output is correct
12 Correct 94 ms 21276 KB Output is correct
13 Correct 118 ms 22092 KB Output is correct
14 Correct 134 ms 23136 KB Output is correct
15 Correct 151 ms 23524 KB Output is correct
16 Correct 158 ms 24536 KB Output is correct
17 Correct 143 ms 25836 KB Output is correct
18 Correct 173 ms 24952 KB Output is correct
19 Correct 154 ms 26868 KB Output is correct
20 Correct 94 ms 20704 KB Output is correct
21 Correct 84 ms 20936 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 14 ms 14824 KB Output is correct
2 Correct 17 ms 14848 KB Output is correct
3 Correct 15 ms 14848 KB Output is correct
4 Correct 14 ms 14976 KB Output is correct
5 Correct 14 ms 14976 KB Output is correct
6 Correct 17 ms 14848 KB Output is correct
7 Correct 15 ms 14880 KB Output is correct
8 Correct 18 ms 14976 KB Output is correct
9 Correct 14 ms 14848 KB Output is correct
10 Correct 13 ms 14848 KB Output is correct
11 Correct 82 ms 20548 KB Output is correct
12 Correct 94 ms 21276 KB Output is correct
13 Correct 118 ms 22092 KB Output is correct
14 Correct 134 ms 23136 KB Output is correct
15 Correct 151 ms 23524 KB Output is correct
16 Correct 158 ms 24536 KB Output is correct
17 Correct 143 ms 25836 KB Output is correct
18 Correct 173 ms 24952 KB Output is correct
19 Correct 154 ms 26868 KB Output is correct
20 Correct 94 ms 20704 KB Output is correct
21 Correct 84 ms 20936 KB Output is correct
22 Correct 491 ms 28712 KB Output is correct
23 Correct 325 ms 27616 KB Output is correct
24 Correct 311 ms 27756 KB Output is correct
25 Correct 382 ms 31080 KB Output is correct
26 Correct 361 ms 28524 KB Output is correct
27 Correct 304 ms 27668 KB Output is correct
28 Correct 63 ms 19576 KB Output is correct
29 Correct 129 ms 23152 KB Output is correct
30 Correct 124 ms 23660 KB Output is correct
31 Correct 125 ms 23188 KB Output is correct
32 Correct 192 ms 26604 KB Output is correct