UOJ #67 新年的毒瘤

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

const int N = 1e5 + 10;
int n, m, tot, r[N], deg[N], sum, cut[N], low[N], dfn[N], tim;

struct edge {int t, n;} e[N * 2];

void add(int x, int y) {
    e[++ tot].t = y; e[tot].n = r[x]; r[x] = tot;
}

void dfs(int u, int per) {
    int chi = 0;
    dfn[u] = low[u] = ++ tim;
    for (int i = r[u]; i; i = e[i].n) {
        int v = e[i].t;
        if (!dfn[v]) {
            chi ++;
            dfs(v, u);
            low[u] = min(low[u], low[v]);
            if (low[v] >= dfn[u]) cut[u] = 1;
        } else if (v != per) {
            low[u] = min(low[u], low[v]);
        }
    }
    if (u == 1 && chi == 1) cut[u] = 0;
}

int main() {
    scanf("%d %d", &n, &m);
    for (int i = 1; i <= m; i ++) {
        int u, v;
        scanf("%d %d", &u, &v);
        deg[u] ++, deg[v] ++;
        add(u, v), add(v, u);
    }
    if (m == n - 1) {
        for (int i = 1; i <= n; i ++) if (deg[i] == 1) sum ++;
        printf("%d\n", sum);
        for (int i = 1; i <= n; i ++) if (deg[i] == 1) printf("%d ", i);
    } else if (m == n - 2) {
        puts("1");
        for (int i = 1; i <= n; i ++) if (!deg[i]) printf("%d", i);
    } else {
        dfs(1, 0);
        for (int i = 1; i <= n; i ++) if (!cut[i] && deg[i] == m - n + 2) sum ++;
        printf("%d\n", sum);
        for (int i = 1; i <= n; i ++) if (!cut[i] && deg[i] == m - n + 2) printf("%d ", i);
    }
    return 0;
}