博客题解174ms:

#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn=100233,maxm=1002333;
struct zs{
    int to,pre;
}e[maxm << 1],e1[maxm << 1];int tot,last[maxn],tot1,last1[maxn];
int u[maxm],v[maxm];
int fa[maxn];
int i,j,k,n,m;
  
inline void insert(int a,int b){
     if(e[last[a]].to==b)return;
     e[++tot].to=b,e[tot].pre=last[a],last[a]=tot;
 }
 inline void ins(int a,int b){
     e1[++tot1].to=b,e1[tot1].pre=last1[a],last1[a]=tot1;
}
int getfa(int x){
   return fa[x]!=x?fa[x]=getfa(fa[x]):x;
}
   
void dfs(int x){
    fa[x]=x+1;
    printf("%d\n",x);
    int next=getfa(1);
      
    for(int i=last[x];i;i=e[i].pre){
        while(next < e[i].to)
           dfs(next),next=getfa(next+1);
         if(next==e[i].to)next=getfa(next+1);
     }
    while(next <=n)dfs(next),next=getfa(next+1);
}
  
int ra;char rx;
inline int read(){
    rx=getchar(),ra=0;
    while(rx < '0'||rx > '9')rx=getchar();
    while(rx >= '0'&&rx <= '9')ra*=10,ra+=rx-48,rx=getchar();return ra;
}
 int main(){
    n=read(),m=read();
    for(i=1;i<=m;i++)u[i]=read(),v[i]=read(),ins(v[i],i),ins(u[i],i);
    for(i=n;i;fa[i]=i,i--)
        for(j=last1[i];j;j=e1[j].pre)
            if(j&1)insert(u[e1[j].to],i);
            else insert(v[e1[j].to],i);
//  for(i=1;i<=n;i++)for(j=last[i];j;j=e[j].pre)printf("%d-->%d\n",i,e[j].to);return 233;
   fa[n+1]=n+1;
     dfs(1);
     return 0;
}

千问AI题解640ms:

#include <cstdio>
#include <vector>
#include <unordered_set>
#include <set>
#include <stack>
 
using namespace std;
 
int main() {
    int n, m;
    scanf("%d %d", &n, &m);
 
    vector<unordered_set<int>> deleted(n + 1);
    for (int i = 0; i < m; ++i) {
        int a, b;
        scanf("%d %d", &a, &b);
        if (a != b) {
            deleted[a].insert(b);
            deleted[b].insert(a);
        }
    }
 
    set<int> available;
    for (int i = 2; i <= n; ++i) {
        available.insert(i);
    }
 
    printf("1\n");
 
    stack<pair<int, int>> stk;
    stk.push({1, 0});
 
    while (!stk.empty()) {
        pair<int, int> current = stk.top();
        int u = current.first;
        int last_v = current.second;
        stk.pop();
 
        set<int>::iterator it = available.upper_bound(last_v);
        while (it != available.end()) {
            int v = *it;
            if (deleted[u].find(v) == deleted[u].end()) {
                available.erase(v);
                printf("%d\n", v);
                stk.push({u, v});
                stk.push({v, 0});
                break;
            }
            ++it;
        }
    }
 
    return 0;
}

博客题解174ms:

#include<cstdio>
 #include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn=100233,maxm=1002333;
struct zs{
    int too,pre;
}e[maxm<<1],e1[maxm<<1];int tot,last[maxn],tot1,last1[maxn];
int u[maxm],v[maxm];
int fa[maxn];
int i,j,k,n,m;
  
inline void insert(int a,int b){
     if(e[last[a]].too==b)return;
     e[++tot].too=b,e[tot].pre=last[a],last[a]=tot;
 }
 inline void ins(int a,int b){
     e1[++tot1].too=b,e1[tot1].pre=last1[a],last1[a]=tot1;
}
int getfa(int x){
   return fa[x]!=x?fa[x]=getfa(fa[x]):x;
}
   
void dfs(int x){
    fa[x]=x+1;
    printf("%d\n",x);
    int next=getfa(1);//printf("  next:%d\n",next);
      
    for(int i=last[x];i;i=e[i].pre){
        while(next<e[i].too)
           dfs(next),next=getfa(next+1);
         if(next==e[i].too)next=getfa(next+1);
     }
    while(next<=n)dfs(next),next=getfa(next+1);
}
  
int ra;char rx;
inline int read(){
    rx=getchar(),ra=0;
    while(rx<'0'||rx>'9')rx=getchar();
    while(rx>='0'&&rx<='9')ra*=10,ra+=rx-48,rx=getchar();return ra;
}
 int main(){
    n=read(),m=read();
    for(i=1;i<=m;i++)u[i]=read(),v[i]=read(),ins(v[i],i),ins(u[i],i);
    for(i=n;i;fa[i]=i,i--)
        for(j=last1[i];j;j=e1[j].pre)
            if(j&1)insert(u[e1[j].too],i);
            else insert(v[e1[j].too],i);
//  for(i=1;i<=n;i++)for(j=last[i];j;j=e[j].pre)printf("%d-->%d\n",i,e[j].too);//return 233;
   fa[n+1]=n+1;
     dfs(1);
     return 0;
 }

千问AI题解640ms:

#include <cstdio>
#include <vector>
#include <unordered_set>
#include <set>
#include <stack>
using namespace std;
int main() {
// 禁用同步以提升性能（对 cin 有效，但保留不影响）
// 注意：对于 scanf/printf，此设置无效
// 保留以兼容旧代码风格
// ios::sync_with_stdio(False);
// cin.tie(Noneptr);
int n, m;
scanf("%d %d", &amp;n, &amp;m);

vector&lt;unordered_set&lt;int&gt;&gt; deleted(n + 1);
for (int i = 0; i &lt; m; ++i) {
    int a, b;
    scanf("%d %d", &amp;a, &amp;b);
    if (a != b) {
        deleted[a].insert(b);
        deleted[ b].insert(a);
    }
}

set&lt;int&gt; available;
for (int i = 2; i &lt;= n; ++i) {
    available.insert(i);
}

printf("1\n");

stack&lt;pair&lt;int, int&gt;&gt; stk;
stk.push({1, 0});

while (!stk.empty()) {
    pair&lt;int, int&gt; current = stk.top();
    int u = current.first;
    int last_v = current.second;
    stk.pop();

    set&lt;int&gt;::iterator it = available.upper_bound(last_v);
    while (it != available.end()) {
        int v = *it;
        if (deleted[ u].find(v) == deleted[ u].end()) {
            available.erase(v);
            printf("%d\n", v);
            stk.push({u, v});
            stk.push({v, 0});
            break;
        }
        ++it;
    }
}

return 0;

}