欧拉通路是否存在

#include <iostream>
#include <cstring>
#include <vector>
#define DEBUG
using namespace std;

const int MAX = 10240;

int N, M, pCnt[MAX];
int pMap[MAX][MAX];
vector<int> pVec;
vector<bool>state(7,false);
void dfs(int x);
void Euler_Circuit();
vector<int>tmp;
bool flag = false;
int main()
{
#ifdef DEBUG
    FILE *in;
    FILE *out;
    freopen_s(&in, "in.txt", "r", stdin);
    freopen_s(&out, "out.txt", "w", stdout);
#endif
    cin >> N >> M;
    memset(pMap, 0, sizeof(pMap));
    for (int i = 1; i <= M; i++)
    {
        int s, e;
        cin >> s >> e;
        pMap[s][e] = pMap[e][s] = 1;    // 无向图
    }
    Euler_Circuit();
    if (flag)cout << "true" << endl;
    else cout << "false" << endl;
#ifdef DEBUG
    fclose(in);
    fclose(out);
#endif
    return 0;
}

void Euler_Circuit()
{
    int nStart = 1, nOddNum = 0;    // nStart保存起点，nOddNum保存有几个顶点有奇数度
    memset(pCnt, 0, sizeof(pCnt));
    for (int i = 1; i <= N; i++)
    {
        for (int j = 1; j <= N; j++)
        {
            pCnt[i] += pMap[i][j];        // 计算各个顶点的度
        }
    }

    for (int i = 1; i <= N; i++)    // 统计奇数度顶点的个数
    {
        if (pCnt[i] & 1)
        {
            nStart = i;
            
            nOddNum++;
        }
    }
    for (int i = 1; i <= N; i++)
    {
        bool flag = false;
        if (pCnt[i] == 1)
        {
            if (!flag)
            {
                nStart = i;
                flag = true;
            }
            
            tmp.push_back(i);
        }
    }
    if (tmp.size() >2 || tmp.size()==1)return;
    pMap[tmp[0]][tmp[1]] = 1;
    pMap[tmp[1]][tmp[0]] = 1;
    if (nOddNum == 1)        
    {
        return;
    }
    else
    {
        if (!tmp.size())
        {
            for (int i = 1; i <= N; i++)
            {
                dfs(i);
            }
        }
        else
        {
            dfs(nStart);
        }
        
    }
}

void dfs(int x)
{
    if (pVec.size() == N && !flag)
    {
        flag = true;
        for (int i = 0; i < N; i++)
        {
            cout << pVec[i] << " ";
        }
        cout << endl;
    }
    if (state[x])return;
    for (int i = 1; i <= N; i++)
    {
        if (pMap[x][i] != 0)
        {
            state[x] = true;
            pVec.push_back(x);
            dfs(i);
            state[x] = false;
            pVec.pop_back();
        }
    }
    
}