oj.uz

Submission #132340

# Submission time Handle Problem Language Result Execution time Memory
132340 2019-07-18T17:46:08 Z Bench0310 One-Way Streets (CEOI17_oneway) C++17
100 / 100
 329 ms 33832 KB 
#include <bits/stdc++.h>

using namespace std;
const int N=100005;
const int M=100005;

vector<pair<int,int>> v[N];
vector<pair<int,int>> edges;
vector<int> depth(N,-1);
vector<vector<int>> par(N,vector<int>(18,-1));
vector<int> bridge_cnt(N,0);
vector<bool> bridge(M,0);
vector<bool> span(M,0); //span-edge
vector<int> up(N,-1); //index of edge connecting vertex i and parent of i
string res(M,'B');
vector<int> id(N,0); //id in the merged graph
vector<pair<int,int>> g[N]; //merged graph
vector<bool> done(N,0); //already directed

void dfs1(int a,int p=-1)
{
    depth[a]=(p!=-1?depth[p]+1:0);
    for(pair<int,int> t:v[a])
    {
        int to=t.first;
        if(t.second==up[a]) continue;
        if(depth[to]==-1)
        {
            span[t.second]=1;
            up[to]=t.second;
            dfs1(to,a);
            bridge_cnt[a]+=bridge_cnt[to];
        }
        else if(a!=to) bridge_cnt[a]+=((depth[a]>depth[to])?1:-1);
    }
}

void dfs2(int a,int idx)
{
    id[a]=idx;
    for(pair<int,int> t:v[a])
    {
        if(bridge[t.second]) continue;
        int to=t.first;
        if(id[to]==0) dfs2(to,idx);
    }
}

void dfs3(int a,int p=-1)
{
    depth[a]=(p!=-1?depth[p]+1:0);
    par[a][0]=p;
    for(int i=1;i<18;i++)
    {
        if(par[a][i-1]==-1) break;
        par[a][i]=par[par[a][i-1]][i-1];
    }
    for(pair<int,int> t:g[a])
    {
        int to=t.first;
        if(to==p) continue;
        up[to]=t.second;
        dfs3(to,a);
    }
}

int lca(int a,int b)
{
    if(depth[a]<depth[b]) swap(a,b);
    for(int i=17;i>=0;i--)
    {
        if(par[a][i]!=-1&&depth[par[a][i]]>=depth[b])
        {
            a=par[a][i];
        }
    }
    if(a==b) return a;
    for(int i=17;i>=0;i--)
    {
        if(par[a][i]!=-1&&par[b][i]!=-1&&par[a][i]!=par[b][i])
        {
            a=par[a][i];
            b=par[b][i];
        }
    }
    return par[a][0];
}

void solve(int a,int b,bool dir) //0-up,1-down
{
    int now=depth[b]-depth[a];
    if(now==0||done[a]) return;
    int c=a;
    int d=par[a][0];
    if(dir) swap(c,d);
    if(c==id[edges[up[a]].first]) res[up[a]]='R';
    else res[up[a]]='L';
    done[a]=1;
    solve(par[a][0],b,dir);
}

int main()
{
    //Graph input
    int n,m;
    scanf("%d%d",&n,&m);
    for(int i=0;i<m;i++)
    {
        int a,b;
        scanf("%d%d",&a,&b);
        v[a].push_back(make_pair(b,i));
        v[b].push_back(make_pair(a,i));
        edges.push_back(make_pair(a,b));
    }
    //Initialize
    for(int i=1;i<=n;i++) if(depth[i]==-1) dfs1(i,-1);
    //Find bridges
    for(int i=0;i<m;i++)
    {
        int a,b;
        tie(a,b)=edges[i];
        if(depth[a]<depth[b]) swap(a,b);
        if(span[i]&&bridge_cnt[a]==0) bridge[i]=1;
    }
    //Merge cycles
    int num=1;
    for(int i=0;i<m;i++)
    {
        if(bridge[i])
        {
            int a,b;
            tie(a,b)=edges[i];
            if(id[a]==0) dfs2(a,num++);
            if(id[b]==0) dfs2(b,num++);
        }
    }
    //Build merged graph
    for(int i=0;i<m;i++)
    {
        if(bridge[i])
        {
            int a,b;
            tie(a,b)=edges[i];
            g[id[a]].push_back(make_pair(id[b],i));
            g[id[b]].push_back(make_pair(id[a],i));
        }
    }
    //Set up merged graph
    fill(depth.begin(),depth.end(),-1);
    fill(up.begin(),up.end(),-1);
    for(int i=1;i<num;i++) if(depth[i]==-1) dfs3(i,-1);
    //Solve
    int z;
    scanf("%d",&z);
    vector<pair<int,int>> q;
    vector<pair<int,int>> one;
    vector<int> two;
    for(int i=0;i<z;i++)
    {
        int a,b;
        scanf("%d%d",&a,&b);
        a=id[a];
        b=id[b];
        int c=lca(a,b);
        q.push_back(make_pair(depth[c],i));
        one.push_back(make_pair(a,b));
        two.push_back(c);
    }
    sort(q.begin(),q.end());
    for(int i=0;i<z;i++)
    {
        int now=q[i].second;
        solve(one[now].first,two[now],0);
        solve(one[now].second,two[now],1);
    }
    for(int i=0;i<m;i++) printf("%c",res[i]);
    printf("\n");
    return 0;
}

Compilation message

oneway.cpp: In function 'int main()':
oneway.cpp:106:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d",&n,&m);
     ~~~~~^~~~~~~~~~~~~~
oneway.cpp:110:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",&a,&b);
         ~~~~~^~~~~~~~~~~~~~
oneway.cpp:154:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&z);
     ~~~~~^~~~~~~~~
oneway.cpp:161:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",&a,&b);
         ~~~~~^~~~~~~~~~~~~~

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 21 ms 17016 KB Output is correct
2 Correct 21 ms 16888 KB Output is correct
3 Correct 21 ms 17016 KB Output is correct
4 Correct 22 ms 17016 KB Output is correct
5 Correct 21 ms 17016 KB Output is correct
6 Correct 22 ms 17016 KB Output is correct
7 Correct 21 ms 17016 KB Output is correct
8 Correct 22 ms 17016 KB Output is correct
9 Correct 21 ms 16888 KB Output is correct
10 Correct 21 ms 17016 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 21 ms 17016 KB Output is correct
2 Correct 21 ms 16888 KB Output is correct
3 Correct 21 ms 17016 KB Output is correct
4 Correct 22 ms 17016 KB Output is correct
5 Correct 21 ms 17016 KB Output is correct
6 Correct 22 ms 17016 KB Output is correct
7 Correct 21 ms 17016 KB Output is correct
8 Correct 22 ms 17016 KB Output is correct
9 Correct 21 ms 16888 KB Output is correct
10 Correct 21 ms 17016 KB Output is correct
11 Correct 80 ms 22636 KB Output is correct
12 Correct 90 ms 23260 KB Output is correct
13 Correct 95 ms 24000 KB Output is correct
14 Correct 116 ms 24816 KB Output is correct
15 Correct 123 ms 25164 KB Output is correct
16 Correct 152 ms 26476 KB Output is correct
17 Correct 137 ms 27376 KB Output is correct
18 Correct 152 ms 26468 KB Output is correct
19 Correct 131 ms 28268 KB Output is correct
20 Correct 86 ms 22764 KB Output is correct
21 Correct 85 ms 22544 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 21 ms 17016 KB Output is correct
2 Correct 21 ms 16888 KB Output is correct
3 Correct 21 ms 17016 KB Output is correct
4 Correct 22 ms 17016 KB Output is correct
5 Correct 21 ms 17016 KB Output is correct
6 Correct 22 ms 17016 KB Output is correct
7 Correct 21 ms 17016 KB Output is correct
8 Correct 22 ms 17016 KB Output is correct
9 Correct 21 ms 16888 KB Output is correct
10 Correct 21 ms 17016 KB Output is correct
11 Correct 80 ms 22636 KB Output is correct
12 Correct 90 ms 23260 KB Output is correct
13 Correct 95 ms 24000 KB Output is correct
14 Correct 116 ms 24816 KB Output is correct
15 Correct 123 ms 25164 KB Output is correct
16 Correct 152 ms 26476 KB Output is correct
17 Correct 137 ms 27376 KB Output is correct
18 Correct 152 ms 26468 KB Output is correct
19 Correct 131 ms 28268 KB Output is correct
20 Correct 86 ms 22764 KB Output is correct
21 Correct 85 ms 22544 KB Output is correct
22 Correct 329 ms 31312 KB Output is correct
23 Correct 284 ms 29628 KB Output is correct
24 Correct 245 ms 29932 KB Output is correct
25 Correct 317 ms 33832 KB Output is correct
26 Correct 308 ms 30572 KB Output is correct
27 Correct 322 ms 29804 KB Output is correct
28 Correct 80 ms 23916 KB Output is correct
29 Correct 134 ms 25744 KB Output is correct
30 Correct 138 ms 26348 KB Output is correct
31 Correct 131 ms 26588 KB Output is correct
32 Correct 199 ms 28396 KB Output is correct