제출 #1251139

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1251139		minhpk	One-Way Streets (CEOI17_oneway)	C++20	0 / 100	3 ms	5444 KiB

oneway

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

const int NMAX = 100005;

int a, b;
vector<pair<int,int>> z[NMAX];
pair<int,int> edge[NMAX];

int id[NMAX], low[NMAX];
int cnt = 0;
int check[NMAX];

bool vis[NMAX];

int ver = 0;
int par[NMAX], sz[NMAX];
int mark[NMAX];

struct node {
    int x, id, flip;
};
vector<node> z1[NMAX];

pair<int,int> rev[NMAX];
int ans[NMAX];

int high[NMAX];
int up[NMAX][25];
int sta[NMAX], fin[NMAX], tour = 0;


void dfs(int i, int parent) {
    cnt++;
    id[i] = low[i] = cnt;
    for (auto p : z[i]) {
        int nxt = p.first, eId = p.second;
        if(nxt == parent) continue;
        if(id[nxt])
            low[i] = min(low[i], id[nxt]);
        else {
            dfs(nxt, i);
            low[i] = min(low[i], low[nxt]);
            if(low[nxt] >= id[i])
                check[eId] = 1;
        }
    }
}


int findUF(int u) {
    return (par[u] == u ? u : par[u] = findUF(par[u]));
}
void joinUF(int x, int y) {
    x = findUF(x);
    y = findUF(y);
    if(x == y) return;
    if(sz[x] < sz[y]) swap(x, y);
    sz[x] += sz[y];
    par[y] = x;
}


void predfs(int i, int parent) {
    tour++;
    sta[i] = tour;
    up[i][0] = parent;
    for (auto p : z1[i]) {
        if(p.x == parent) continue;
        high[p.x] = high[i] + 1;
        rev[p.x] = {p.id, p.flip};
        predfs(p.x, i);
    }
    fin[i] = tour;
}

bool isanc(int x, int y) {
    return sta[x] <= sta[y] && fin[x] >= fin[y];
}


int LCA(int u, int v) {
    if(high[u] < high[v]) swap(u, v);
    for (int i = 20; i >= 0; i--) {
        if(high[u] - (1LL << i) >= high[v])
            u = up[u][i];
    }
    if(u == v) return u;
    for (int i = 20; i >= 0; i--) {
        if(up[u][i] != up[v][i]) {
            u = up[u][i];
            v = up[v][i];
        }
    }
    return up[u][0];
}


int diff[NMAX];



signed main(){
    if (fopen("oneway.inp","r")){
        freopen("oneway.inp","r",stdin);
        freopen("oneway.out","w",stdout);
    }
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    cin >> a >> b;
    for (int i = 1; i <= b; i++){
        int x, y;
        cin >> x >> y;
        z[x].push_back({y, i});
        z[y].push_back({x, i});
        edge[i] = {x, y};
    }


    for (int i = 1; i <= a; i++){
        if(!id[i])
            dfs(i, 0);
    }


    for (int i = 1; i <= a; i++){
        par[i] = i;
        sz[i] = 1;
    }
    for (int i = 1; i <= b; i++){
        if(!check[i])
            joinUF(edge[i].first, edge[i].second);
    }


    for (int i = 1; i <= a; i++){
        int x = findUF(i);
        if(!vis[x]){
            vis[x] = true;
            ver++;
            mark[x] = ver;
        }
        mark[i] = mark[x];
    }


    for (int i = 1; i <= b; i++){
        int x = mark[ edge[i].first ];
        int y = mark[ edge[i].second ];
        if(x == y) continue;

        z1[x].push_back({y, i, 1});
        z1[y].push_back({x, i, -1});
    }


    for (int i = 1; i <= ver; i++){
        if(sta[i] == 0){
            high[i] = 0;
            predfs(i, 0);
        }
    }


    for (int j = 1; j <= 20; j++){
        for (int i = 1; i <= ver; i++){
            int parNode = up[i][j-1];
            if(parNode == 0)
                up[i][j] = 0;
            else
                up[i][j] = up[ parNode ][j-1];
        }
    }


    for (int i = 1; i <= ver; i++) diff[i] = 0;

    int q;
    cin >> q;
    for (int i = 1; i <= q; i++){
        int u, v;
        cin >> u >> v;
        int u_ = mark[u], v_ = mark[v];
        if(u_ == v_) continue;
        int L = LCA(u_, v_);

        diff[u_] += 1;
        diff[v_] -= 1;
        diff[L] -= 1;
        int parL = up[L][0];
        if(parL != 0) diff[parL] -= 1;
    }


    vector<pair<int,int>> order;
    for (int i = 1; i <= ver; i++){
        order.push_back({high[i], i});
    }
    sort(order.begin(), order.end(), greater<pair<int,int>>());
    for (auto &p : order){
        int node = p.second;
        int parNode = up[node][0];
        if(parNode != 0)
            diff[parNode] += diff[node];
    }


    for (int i = 2; i <= ver; i++){
        int parNode = up[i][0];
        if(parNode == 0) continue;
        int eId = rev[i].first;
        int val = diff[i];
        if(val * rev[i].second > 0)
            ans[eId] = 1;
        else if(val * rev[i].second < 0)
            ans[eId] = -1;
        else
            ans[eId] = 0;
    }


    for (int i = 1; i <= b; i++){
        if(ans[i] == 0)
            cout << "B";
        else if(ans[i] < 0)
            cout << "R";
        else
            cout << "L";
    }

    return 0;
}






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

/*
freopen("test.txt", "r", stdin);
    freopen("o2.out", "w", stdout);
*/

/*
10 3 2 2
1 1 0
1 1 0
0 1 1
1 0 0
1 1 0
1 0 1
1 0 1
1 1 0
0 0 1
0 1 1
0
0
*/

컴파일 시 표준 에러 (stderr) 메시지

oneway.cpp: In function 'int main()':
oneway.cpp:106:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  106 |         freopen("oneway.inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:107:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  107 |         freopen("oneway.out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 30
• Subtask 2: 0 / 30
• Subtask 3: 0 / 40