Submission #825010

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
825010	2023-08-14T13:19:04 Z	jamezzz	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	289 ms	32920 KB

oneway

#include <bits/stdc++.h>
using namespace std;

#ifdef DEBUG
#define dbg(...) printf(__VA_ARGS__);
#define getchar_unlocked getchar
#else
#define dbg(...)
#endif
#define sf scanf
#define pf printf
#define fi first
#define se second
#define pb push_back
#define psf push_front
#define ppb pop_back
#define ppf pop_front
#define sz(x) (int)x.size()
#define mnto(x,y) x=min(x,(__typeof__(x))y)
#define mxto(x,y) x=max(x,(__typeof__(x))y)
#define INF 1023456789
#define LINF 1023456789123456789
#define all(x) x.begin(),x.end()
#define lb(x,v) (lower_bound(all(x),v)-x.begin())
#define ub(x,v) (upper_bound(all(x),v)-x.begin())
#define disc(x) sort(all(x));x.resize(unique(all(x))-x.begin());
typedef long long ll;
typedef long double ld;
typedef pair<int,int> ii;
typedef pair<ll,ll> pll;
typedef tuple<int,int,int> iii;
typedef tuple<int,int,int,int> iiii;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<ii> vii;
mt19937 rng(time(0));

#define mod 1000000007

inline int add(int a,int b){
	int r=a+b;
	while(r>=mod)r-=mod;
	while(r<0)r+=mod;
	return r;
}

inline int mult(int a,int b){
	return (int)(((ll)(a*b))%mod);
}

inline int rd(){
	int x=0;
	char ch=getchar_unlocked();
	while(!(ch&16))ch=getchar_unlocked();//keep reading while current character is whitespace
    while(ch&16){//this will break when ‘\n’ or ‘ ‘ is encountered
		x=(x<<3)+(x<<1)+(ch&15);
		ch=getchar_unlocked();
	}
	return x;
}

#define maxn 100005

int n,m,a[maxn],b[maxn],q,x[maxn],y[maxn];
int num[maxn],par[maxn],low[maxn],cnt,bridge[maxn];
int upar[maxn],bcnt,bcc[maxn];
int p[20][maxn],vis[maxn],dep[maxn];
ii to[maxn];
char ans[maxn];
stack<int> s;
vector<ii> AL[maxn],AL2[maxn];

void dfs(int u){
	num[u]=low[u]=cnt++;
	s.push(u);
	for(auto[v,i]:AL[u]){
		if(num[v]==-1){
			par[v]=u;
			dfs(v);
			low[u]=min(low[u],low[v]);
			if(low[v]>num[u]){
				bridge[i]=true;
			}
		}
		else if(v!=par[u]){
			low[u]=min(low[u],num[v]);
		}
	}
}

int fp(int i){
	return upar[i]==i?i:upar[i]=fp(upar[i]);
}

void join(int x,int y){
	upar[fp(x)]=fp(y);
}

void dfs2(int u){
	vis[u]=true;
	for(int k=1;k<20;++k){
		if(p[k-1][u]!=-1)p[k][u]=p[k-1][p[k-1][u]];
	}
	for(auto[v,i]:AL2[u]){
		if(p[0][u]==v)continue;
		p[0][v]=u;
		dep[v]=dep[u]+1;
		dfs2(v);
	}
}

int lca(int a,int b){
	if(dep[a]<dep[b])swap(a,b);
	for(int k=19;k>=0;--k){
		if(p[k][a]!=-1&&dep[p[k][a]]>=dep[b])a=p[k][a];
	}
	if(a==b)return a;
	for(int k=19;k>=0;--k){
		if(p[k][a]!=p[k][b])a=p[k][a],b=p[k][b];
	}
	return p[0][a];
}

//returns dep to, dir
ii dfs3(int u){
	ii res=to[u];
	for(auto[v,i]:AL2[u]){
		if(p[0][u]==v)continue;
		ii pr=dfs3(v);
		if(pr.fi<=dep[u]){
			if(pr.se==0){//up
				if(bcc[a[i]]==v)ans[i]='R';
				else ans[i]='L';
			}
			else{//down
				if(bcc[a[i]]==u)ans[i]='R';
				else ans[i]='L';
			}
		}
		else ans[i]='B';
		res=min(res,pr);
	}
	return res;
}

int main(){
	sf("%d%d",&n,&m);
	for(int i=0;i<m;++i){
		sf("%d%d",&a[i],&b[i]);
		AL[a[i]].pb({b[i],i});
		AL[b[i]].pb({a[i],i});
	}
	sf("%d",&q);
	for(int i=0;i<q;++i){
		sf("%d%d",&x[i],&y[i]);
	}
	memset(num,-1,sizeof num);
	for(int i=1;i<=n;++i){
		if(num[i]==-1){
			dfs(i);
			if(sz(AL[i])==1){
				bridge[AL[i][0].se]=true;
			}
		}
		upar[i]=i;
	}
	for(int i=0;i<m;++i){
		if(!bridge[i]){
			join(a[i],b[i]);
		}
	}
	for(int i=1;i<=n;++i){
		if(fp(i)==i)bcc[i]=bcnt++;
	}
	for(int i=1;i<=n;++i){
		bcc[i]=bcc[fp(i)];
	}
	for(int i=0;i<m;++i){
		if(bcc[a[i]]==bcc[b[i]]){
			ans[i]='B';
		}
		else{
			int u=bcc[a[i]],v=bcc[b[i]];
			AL2[u].pb({v,i});
			AL2[v].pb({u,i});
		}
	}
	memset(p,-1,sizeof p);
	for(int i=0;i<bcnt;++i){
		if(!vis[i])dfs2(i);
		to[i]={dep[i],2};
	}
	for(int i=0;i<q;++i){
		int u=bcc[x[i]],v=bcc[y[i]];
		int l=lca(u,v);
		if(u!=l){
			to[u]=min(to[u],{dep[l],0});//up
		}
		if(v!=l){
			to[v]=min(to[v],{dep[l],1});//down
		}
	}
	for(int i=0;i<bcnt;++i){
		if(p[0][i]==-1)dfs3(i);
	}
	for(int i=0;i<m;++i)pf("%c",ans[i]);
	pf("\n");
}

/*
5 6
1 2
1 2
4 3
2 3
1 3
5 1
2
4 5
1 3

9 11
9 1
1 2
2 9
1 3
3 4
4 5
5 6
6 4
2 7
7 8
7 8
3
7 3
1 3
4 3
*/

Compilation message

oneway.cpp: In function 'int main()':
oneway.cpp:147:4: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  147 |  sf("%d%d",&n,&m);
      |    ^
oneway.cpp:149:5: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  149 |   sf("%d%d",&a[i],&b[i]);
      |     ^
oneway.cpp:153:4: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  153 |  sf("%d",&q);
      |    ^
oneway.cpp:155:5: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  155 |   sf("%d%d",&x[i],&y[i]);
      |     ^

Subtask #1

30.0 / 30.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	7 ms	13268 KB	Output is correct
2	Correct	6 ms	13268 KB	Output is correct
3	Correct	7 ms	13268 KB	Output is correct
4	Correct	8 ms	13340 KB	Output is correct
5	Correct	7 ms	13396 KB	Output is correct
6	Correct	7 ms	13272 KB	Output is correct
7	Correct	8 ms	13340 KB	Output is correct
8	Correct	8 ms	13396 KB	Output is correct
9	Correct	6 ms	13340 KB	Output is correct
10	Correct	7 ms	13236 KB	Output is correct

Subtask #2

30.0 / 30.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	7 ms	13268 KB	Output is correct
2	Correct	6 ms	13268 KB	Output is correct
3	Correct	7 ms	13268 KB	Output is correct
4	Correct	8 ms	13340 KB	Output is correct
5	Correct	7 ms	13396 KB	Output is correct
6	Correct	7 ms	13272 KB	Output is correct
7	Correct	8 ms	13340 KB	Output is correct
8	Correct	8 ms	13396 KB	Output is correct
9	Correct	6 ms	13340 KB	Output is correct
10	Correct	7 ms	13236 KB	Output is correct
11	Correct	41 ms	19572 KB	Output is correct
12	Correct	50 ms	20880 KB	Output is correct
13	Correct	54 ms	22316 KB	Output is correct
14	Correct	60 ms	24112 KB	Output is correct
15	Correct	106 ms	24652 KB	Output is correct
16	Correct	155 ms	26768 KB	Output is correct
17	Correct	131 ms	28100 KB	Output is correct
18	Correct	128 ms	26772 KB	Output is correct
19	Correct	113 ms	29128 KB	Output is correct
20	Correct	46 ms	20360 KB	Output is correct
21	Correct	48 ms	20532 KB	Output is correct

Subtask #3

40.0 / 40.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	7 ms	13268 KB	Output is correct
2	Correct	6 ms	13268 KB	Output is correct
3	Correct	7 ms	13268 KB	Output is correct
4	Correct	8 ms	13340 KB	Output is correct
5	Correct	7 ms	13396 KB	Output is correct
6	Correct	7 ms	13272 KB	Output is correct
7	Correct	8 ms	13340 KB	Output is correct
8	Correct	8 ms	13396 KB	Output is correct
9	Correct	6 ms	13340 KB	Output is correct
10	Correct	7 ms	13236 KB	Output is correct
11	Correct	41 ms	19572 KB	Output is correct
12	Correct	50 ms	20880 KB	Output is correct
13	Correct	54 ms	22316 KB	Output is correct
14	Correct	60 ms	24112 KB	Output is correct
15	Correct	106 ms	24652 KB	Output is correct
16	Correct	155 ms	26768 KB	Output is correct
17	Correct	131 ms	28100 KB	Output is correct
18	Correct	128 ms	26772 KB	Output is correct
19	Correct	113 ms	29128 KB	Output is correct
20	Correct	46 ms	20360 KB	Output is correct
21	Correct	48 ms	20532 KB	Output is correct
22	Correct	289 ms	29956 KB	Output is correct
23	Correct	188 ms	28496 KB	Output is correct
24	Correct	152 ms	28692 KB	Output is correct
25	Correct	200 ms	32920 KB	Output is correct
26	Correct	227 ms	29616 KB	Output is correct
27	Correct	182 ms	28516 KB	Output is correct
28	Correct	56 ms	18244 KB	Output is correct
29	Correct	63 ms	21864 KB	Output is correct
30	Correct	62 ms	22196 KB	Output is correct
31	Correct	65 ms	22276 KB	Output is correct
32	Correct	121 ms	26064 KB	Output is correct