hiho 50 Fleury算法求歐拉路徑

問題

http://hihocoder.com/problemset/problem/1181?sid=784004

解法

僞代碼

DFS(u):
    While (u存在未被刪除的邊e(u,v))
        刪除邊e(u,v)
        DFS(v)
    End
    PathSize ← PathSize + 1
    Path[ PathSize ] ← u

#include <bits/stdc++.h>
using namespace std;
enum{maxn = 1000+4, maxm = 5005};
vector<int> G[maxn];
int degree[maxn];
class E{
 public:
    E(int _a, int _b)
    {
        a = min(_a, _b);
        b = max(_a, _b);
    };
    int a, b;
    bool operator<(const E& e)const
    {
        return a==e.a? (b<e.b) : (a<e.a);
    }
};
map<E, int> edgeCnt;
void dfs(int u)
{
    for (int i=0; i< G[u].size(); ++i)
    {
        int v= G[u][i];
        E e(u, v);
        if (edgeCnt[e])
        {
            --edgeCnt[e];
            dfs(v);
        }
    }
    printf("%d ", u);
}
int main()
{
    //freopen("in.txt", "r", stdin);
    int n, m;
    scanf("%d %d", &n, &m);
    memset(degree, 0, sizeof(degree));
    edgeCnt.clear();
    for (int i=0; i< m; ++i)
    {
        int a, b;
        scanf("%d %d", &a, &b);
        G[a].push_back(b);
        G[b].push_back(a);
        ++degree[a];
        ++degree[b];
        ++edgeCnt[E(a, b)];
    }
    int start = 1;
    for (int i=2; i<=n; ++i)
    {
        if (degree[start]==0 || (degree[start]%2 ==0 && degree[i]%2))
            start = i;
        if (degree[start]%2)
            break;
    }
    dfs(start);
    putchar('\n');
    return 0;
}