提出 #71367489

---

ソースコード 拡げる

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

const int N = 300005;
vector<int> adj[N];
int num[N], low[N], ti;
bool h2[N], bad;
int bl[N], ye[N];
bool vis[N];
int p[N];
int par_ear[N];

void dfs(int u, int pa) {
    num[u] = low[u] = ++ti;
    if(u == 2) h2[u] = 1;
    for(int v : adj[u]) {
        if(v == pa) continue;
        if(num[v]) low[u] = min(low[u], num[v]);
        else {
            dfs(v, u);
            low[u] = min(low[u], low[v]);
            if(h2[v]) h2[u] = 1;
            if(low[v] > num[u] && !h2[v]) bad = 1;
        }
    }
}

void get_bb(int s, int t) {
    queue<int> q;
    q.push(s);
    p[s] = -1;
    while(q.size()) {
        int u = q.front(); q.pop();
        if(u == t) break;
        for(int v : adj[u]) {
            if(!p[v]) {
                p[v] = u;
                q.push(v);
            }
        }
    }
}

void get_ear(int s, int fu, vector<int>& qm) {
    queue<int> q;
    q.push(s);
    vector<int> touched;
    par_ear[s] = fu;
    touched.push_back(s);
    int tw = -1;

    while(q.size()) {
        int u = q.front(); q.pop();
        bool found = false;
        for(int v : adj[u]) {
            if(v == fu && u == s) continue;
            if(vis[v]) {
                tw = v;
                par_ear[v] = u;
                touched.push_back(v);
                found = true;
                break;
            }
            if(par_ear[v] == 0) {
                par_ear[v] = u;
                touched.push_back(v);
                q.push(v);
            }
        }
        if(found) break;
    }

    int u = tw;
    int pre = -1;
    while(u != s) {
        int pa = par_ear[u];
        if(!vis[u]) {
            bl[u] = pa;
            if(pre == -1) ye[u] = tw;
            else ye[u] = pre;
            vis[u] = 1;
            qm.push_back(u);
        }
        pre = u;
        u = pa;
    }
    bl[s] = fu;
    ye[s] = pre;
    vis[s] = 1;
    qm.push_back(s);
    for(int x : touched) par_ear[x] = 0;
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    int n, m;
    if(!(cin >> n >> m)) return 0;
    for(int i = 0; i < m; i++){
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    dfs(1, 0);
    if(bad) {
        cout << "No\n";
        return 0;
    }

    cout << "Yes\n";
    get_bb(1, 2);
    vector<int> backbone;
    int curr = 2;
    while(curr != -1) {
        backbone.push_back(curr);
        curr = p[curr];
    }
    reverse(backbone.begin(), backbone.end());

    vector<int> qm;
    for(int i = 0; i < backbone.size(); i++){
        int u = backbone[i];
        vis[u] = 1;
        qm.push_back(u);
        if(i > 0) bl[u] = backbone[i-1];
        if(i < backbone.size() - 1) ye[u] = backbone[i+1];
    }

    int head = 0;
    while(head < qm.size()){
        int u = qm[head++];
        for(int v : adj[u]){
            if(!vis[v]) {
                get_ear(v, u, qm);
            }
        }
    }

    cout << ye[1] << "\n";
    cout << bl[2] << "\n";
    for(int i = 3; i <= n; i++){
        cout << bl[i] << " " << ye[i] << "\n";
    }
    return 0;
}

提出情報

コンパイルエラー

./Main.cpp: In function 'int main()':
./Main.cpp:122:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  122 |     for(int i = 0; i < backbone.size(); i++){
      |                    ~~^~~~~~~~~~~~~~~~~
./Main.cpp:127:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  127 |         if(i < backbone.size() - 1) ye[u] = backbone[i+1];
      |            ~~^~~~~~~~~~~~~~~~~~~~~
./Main.cpp:131:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  131 |     while(head < qm.size()){
      |           ~~~~~^~~~~~~~~~~

ジャッジ結果