CCF_ 201512-4_送货

一道拖了很久了题，用bool开的vis不会爆内存，dfs回溯的话会超时，于是有了一个很巧妙的dfs。

#include<iostream>
#include<cstring>
#include<cstdio>
#include<vector>
#include<queue>
#include<algorithm>
using namespace std;

bool vis[][] = {};
int ans[],n,m,cnt = ;
vector<int> v[];

void dfs(int x)
{
    for(int i = ;i < v[x].size();i++)
    {
        if(vis[x][v[x][i]])   continue;
        vis[x][v[x][i]] = ;
        vis[v[x][i]][x] = ;
        dfs(v[x][i]);
        ans[++cnt] = v[x][i];
    }
}

int main()
{
    scanf("%d%d",&n,&m);
    for(int i = ;i <= m;i++)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        v[x].push_back(y);
        v[y].push_back(x);
    }
    for(int i = ;i <= n;i++)   sort(v[i].begin(),v[i].end());
    dfs();
    if(cnt == m)
    {
        printf("");
        for(int i = cnt;i > ;i--) printf(" %d",ans[i]);
        printf("\n");
    }
    else    printf("-1\n");
    return ;
}