[POJ 1041] John's Trip

[题目链接]

         http://poj.org/problem?id=1041

[算法]

        欧拉回路
[代码]

        

#include <algorithm>  
#include <bitset>  
#include <cctype>  
#include <cerrno>  
#include <clocale>  
#include <cmath>  
#include <complex>  
#include <cstdio>  
#include <cstdlib>  
#include <cstring>  
#include <ctime>  
#include <deque>  
#include <exception>  
#include <fstream>  
#include <functional>  
#include <limits>  
#include <list>  
#include <map>  
#include <iomanip>  
#include <ios>  
#include <iosfwd>  
#include <iostream>  
#include <istream>  
#include <ostream>  
#include <queue>  
#include <set>  
#include <sstream>  
#include <stdexcept>  
#include <streambuf>  
#include <string>  
#include <utility>  
#include <vector>  
#include <cwchar>  
#include <cwctype>  
#include <stack>  
#include <limits.h>
using namespace std;
#define MAXN 2010
#define MAXM 45

int i,u,v,cnt,max_id,id;
int degree[MAXN],ans[MAXN];
bool visited[MAXN];
pair<int,int> e[MAXN];
bool flag;

inline void dfs(int u)
{
        int i,v;
        for (i = 1; i <= max_id; i++)
        {
                if (!visited[i] && (e[i].first == u || e[i].second == u))
                {
                        visited[i] = true;
                        dfs(e[i].first + e[i].second - u);
                        ans[++cnt] = i;
                }        
        }        
}

int main() 
{
        
        while (scanf("%d%d",&u,&v) != EOF)
        {
                if (!u && !v) break;
                max_id = 0;
                memset(degree,false,sizeof(degree));
                memset(visited,false,sizeof(visited));
                scanf("%d",&id);
                max_id = max(max_id,id);
                e[id] = make_pair(u,v);
                degree[u]++; degree[v]++;
                while (scanf("%d%d",&u,&v) && (u || v))
                {
                        scanf("%d",&id);
                        e[id] = make_pair(u,v);
                        max_id = max(max_id,id);
                        degree[u]++; degree[v]++;
                }
                flag = false;
                for (i = 1; i <= 50; i++)
                {
                        if (degree[i] & 1)
                        {
                                flag = true;
                                break;
                        }
                }
                if (flag)
                {
                        printf("Round trip does not exist.\n");
                        continue;
                }
                cnt = 0;
                dfs(1);
                for (i = cnt; i >= 1; i--) printf("%d ",ans[i]);
                printf("\n");
        }
        
        return 0;
    
}