Hierholzers算法

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<ctime>
#include<stack>
using namespace std;
const int N=2005;
int n,a,b,G[N][N],d[N],ans[N],Cnt;
void dfs(int x){
    for(int i=1;i<=500;i++){
		if(G[x][i]){
			G[x][i]--;
			G[i][x]--;
			dfs(i);
		}
	}
    ans[++Cnt]=x;
}
int main(){
    cin>>n; 
    for(int i=1;i<=n;i++){
        cin>>a>>b;
        G[a][b]++;
        G[b][a]++; 
        d[a]++; 
        d[b]++;
    }
    int s=1;
    for(int i=1;i<=500;i++){
		if(d[i]%2==1){
			s=i;
			break;
		}
	}
    dfs(s);
    for(int i=n+1;i>=1;i--){
		cout<<ans[i]<<endl;
	}
	return 0;
}