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Submission #397056

# Submission time Handle Problem Language Result Execution time Memory
397056 2021-05-01T08:59:03 Z Nicholas_Patrick One-Way Streets (CEOI17_oneway) C++17
100 / 100
 266 ms 26812 KB 
#include <cstdio>
#include <queue>
#include <string>
using namespace std;

struct edge{
	int f, t, i;
};
string ans;
//graph 1
vector<vector<edge>> adjLis1;
vector<int> dt, low;
int t;
vector<int> p;
int par(int x){
	if(p[x]==x)
		return x;
	return p[x]=par(p[x]);
}
vector<int> pp;
int ppar(int x){
	if(pp[x]==x)
		return x;
	return pp[x]=ppar(pp[x]);
}
//graph 2
vector<edge> edgeLis;
vector<vector<edge>> adjLis2;
//graph 1: graph 2
void dfs1(int x, int pi=-1){
	dt[x]=low[x]=t++;
	for(auto i: adjLis1[x]){
		int y=i.f+i.t-x;
		if(dt[y]==0){
			dfs1(y, i.i);
			low[x]=min(low[x], low[y]);
			if(dt[x]<low[y]){
				//bridge
				edgeLis.push_back(i);
			}else{
				//not bridge
				p[par(x)]=par(y);
				// printf("merge %d %d\n", x, y);
			}
		}else if(i.i!=pi){
			low[x]=min(low[x], dt[y]);
		}
	}
}
//graph 1
void dfs2(int x){
	dt[x]=1;
	for(auto i: adjLis1[x]){
		int y=i.f+i.t-x;
		if(p[x]==p[y])
			ans[i.i]='B';
		if(dt[y]==0)
			dfs2(y);
	}
}
//graph 2
vector<int> parent, depth, jump;
vector<int> direction;//012 + 048 --> parent/jump nothing, up, down
//yes, I know, p, par, pi, and parent all mean parent
void dfs3(int x){
	for(auto& i: adjLis2[x]){
		int y=i.f+i.t-x;
		if(y==parent[x])
			continue;
		parent[y]=x;
		depth[y]=depth[x]+1;
		int j=jump[x];
		jump[y]=depth[jump[j]]+depth[x]==depth[j]<<1?jump[j]:x;
		dfs3(y);
	}
}
void direct(int x, int y){
	if(depth[x]<depth[y]){
		while(depth[x]<depth[y]){
			if(depth[x]<=depth[jump[y]]){
				direction[y]|=8;
				y=jump[y];
			}else{
				direction[y]|=2;
				y=parent[y];
			}
		}
	}else{
		while(depth[x]>depth[y]){
			if(depth[y]<=depth[jump[x]]){
				direction[x]|=4;
				x=jump[x];
			}else{
				direction[x]|=1;
				x=parent[x];
			}
		}
	}
	if(x==y){
		// printf("LCA a: %d\n", x);
		return;
	}
	while(parent[x]!=parent[y]){
		if(jump[x]!=jump[y]){
			direction[x]|=4;
			x=jump[x];
			direction[y]|=8;
			y=jump[y];
		}else{
			direction[x]|=1;
			x=parent[x];
			direction[y]|=2;
			y=parent[y];
		}
	}
	direction[x]|=1;
	direction[y]|=2;
	// printf("LCA b: %d\n", parent[x]);
}
void dfs4(int x){
	for(auto& i: adjLis2[x]){
		int y=i.f+i.t-x;
		if(y==parent[x])
			continue;
		dfs4(y);
		if(jump[y]!=x){
			direction[x]|=direction[y]&12;
			direction[jump[x]]|=direction[y]&12;
		}
		if(direction[y]&5){
			if(i.f==y){
				ans[i.i]='R';
			}else{
				ans[i.i]='L';
			}
		}
		if(direction[y]&10){
			if(i.f==y){
				ans[i.i]='L';
			}else{
				ans[i.i]='R';
			}
		}
	}
}
int main(){
	int n, m;
	scanf("%d%d", &n, &m);
	ans=string(m, 'B');
	adjLis1.resize(n);
	pp.resize(n);
	for(int i=n; i--;)pp[i]=i;
	for(int i=0; i<m; i++){
		edge inp;
		scanf("%d%d", &inp.f, &inp.t), inp.f--, inp.t--;
		pp[ppar(inp.f)]=ppar(inp.t);
		inp.i=i;
		adjLis1[inp.f].push_back(inp);
		adjLis1[inp.t].push_back(inp);
	}
	dt.assign(n, 0);
	low.resize(n);
	t=1;
	p.resize(n);
	for(int i=n; i--;)p[i]=i;
	for(int i=n; i--;){
		if(ppar(i)==i)
			dfs1(i);
	}
	for(int& i: p)
		i=par(i);
	dt.assign(n, 0);
	for(int i=n; i--;){
		if(pp[i]==i)
			dfs2(i);
	}
	adjLis2.resize(n);
	for(auto i: edgeLis){
		i.f=p[i.f], i.t=p[i.t];
		// printf("edge %d-%d\n", i.f, i.t);
		adjLis2[i.f].push_back(i);
		adjLis2[i.t].push_back(i);
	}
	parent.resize(n);
	jump.resize(n);
	depth.resize(n);
	for(int i=n; i--;){
		if(pp[i]==i){
			int root=p[i];
			parent[root]=jump[root]=root;
			depth[root]=0;
			dfs3(root);
		}
	}
	direction.assign(n, 0);
	int q;
	scanf("%d", &q);
	while(q--){
		int x, y;
		scanf("%d%d", &x, &y), x--, y--;
		x=p[x], y=p[y];
		direct(x, y);
	}
	for(int i=n; i--;){
		if(pp[i]==i){
			int root=p[i];
			dfs4(root);
		}
	}
	printf("%s\n", ans.c_str());
}

Compilation message

oneway.cpp: In function 'int main()':
oneway.cpp:148:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  148 |  scanf("%d%d", &n, &m);
      |  ~~~~~^~~~~~~~~~~~~~~~
oneway.cpp:155:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  155 |   scanf("%d%d", &inp.f, &inp.t), inp.f--, inp.t--;
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:197:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  197 |  scanf("%d", &q);
      |  ~~~~~^~~~~~~~~~
oneway.cpp:200:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  200 |   scanf("%d%d", &x, &y), x--, y--;
      |   ~~~~~^~~~~~~~~~~~~~~~

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 204 KB Output is correct
2 Correct 1 ms 204 KB Output is correct
3 Correct 1 ms 332 KB Output is correct
4 Correct 1 ms 460 KB Output is correct
5 Correct 2 ms 460 KB Output is correct
6 Correct 1 ms 332 KB Output is correct
7 Correct 2 ms 424 KB Output is correct
8 Correct 2 ms 460 KB Output is correct
9 Correct 2 ms 332 KB Output is correct
10 Correct 1 ms 332 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 204 KB Output is correct
2 Correct 1 ms 204 KB Output is correct
3 Correct 1 ms 332 KB Output is correct
4 Correct 1 ms 460 KB Output is correct
5 Correct 2 ms 460 KB Output is correct
6 Correct 1 ms 332 KB Output is correct
7 Correct 2 ms 424 KB Output is correct
8 Correct 2 ms 460 KB Output is correct
9 Correct 2 ms 332 KB Output is correct
10 Correct 1 ms 332 KB Output is correct
11 Correct 52 ms 8528 KB Output is correct
12 Correct 67 ms 10476 KB Output is correct
13 Correct 95 ms 12924 KB Output is correct
14 Correct 125 ms 16104 KB Output is correct
15 Correct 153 ms 17300 KB Output is correct
16 Correct 149 ms 19132 KB Output is correct
17 Correct 145 ms 22864 KB Output is correct
18 Correct 140 ms 19100 KB Output is correct
19 Correct 114 ms 22904 KB Output is correct
20 Correct 78 ms 10308 KB Output is correct
21 Correct 71 ms 9552 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 204 KB Output is correct
2 Correct 1 ms 204 KB Output is correct
3 Correct 1 ms 332 KB Output is correct
4 Correct 1 ms 460 KB Output is correct
5 Correct 2 ms 460 KB Output is correct
6 Correct 1 ms 332 KB Output is correct
7 Correct 2 ms 424 KB Output is correct
8 Correct 2 ms 460 KB Output is correct
9 Correct 2 ms 332 KB Output is correct
10 Correct 1 ms 332 KB Output is correct
11 Correct 52 ms 8528 KB Output is correct
12 Correct 67 ms 10476 KB Output is correct
13 Correct 95 ms 12924 KB Output is correct
14 Correct 125 ms 16104 KB Output is correct
15 Correct 153 ms 17300 KB Output is correct
16 Correct 149 ms 19132 KB Output is correct
17 Correct 145 ms 22864 KB Output is correct
18 Correct 140 ms 19100 KB Output is correct
19 Correct 114 ms 22904 KB Output is correct
20 Correct 78 ms 10308 KB Output is correct
21 Correct 71 ms 9552 KB Output is correct
22 Correct 266 ms 23992 KB Output is correct
23 Correct 232 ms 20092 KB Output is correct
24 Correct 252 ms 20284 KB Output is correct
25 Correct 217 ms 26812 KB Output is correct
26 Correct 225 ms 21788 KB Output is correct
27 Correct 213 ms 20028 KB Output is correct
28 Correct 47 ms 4748 KB Output is correct
29 Correct 107 ms 10840 KB Output is correct
30 Correct 114 ms 10324 KB Output is correct
31 Correct 95 ms 12168 KB Output is correct
32 Correct 152 ms 17152 KB Output is correct