SGU 101 题解

#include<iostream>
#include<algorithm>
using namespace std;
struct sticktype
{
	int l;
	int r;
	bool vis;
}stick[101];
struct pointtype
{
	int amount;
	int next[7];
	bool vis; 
}point[7];
int tail=0;
int queue[201];
void dfs(int p);
int main()
{
	int n;
	cin>>n;
	for(int i=0;i<=6;i++)
	{
		point[i].amount=0;
		for(int j=0;j<=6;j++)
		{
			point[i].next[j]=0;
		}
	}
	for(int i=1;i<=n;i++)
	{
		cin>>stick[i].l>>stick[i].r;
		stick[i].vis=false;
		point[stick[i].l].vis=false;
		point[stick[i].r].vis=false;
		point[stick[i].l].amount++;
		point[stick[i].l].next[stick[i].r]+=1;
		point[stick[i].r].amount++;
		point[stick[i].r].next[stick[i].l]+=1;
	}
	int m=0;
	int res=0;
	for(int i=0;i<=6;i++)
	{
		if(point[i].amount!=0)
		{
			m++;
			if(point[i].amount%2!=0)
			{
				res++;
			}
		}
	}
	if(res!=0&&res!=2)
	{
		cout<<"No solution";
		return 0;
	}
	int begin;
	if(res==0)
	{
		for(int i=0;i<=6;i++)
		{
			if(point[i].amount!=0)
			{
				begin=i;
				break;
			}
		}
	}
	else
	{
		for(int i=0;i<=6;i++)
		{
			if(point[i].amount%2!=0)
			{
				begin=i;
				break;
			}
		}
	}
	dfs(begin);
	for(int i=0;i<=6;i++)
	{
		if(!point[i].vis&&point[i].amount!=0)
		{
			cout<<"No solution";
			return 0;
		}
	}
	for(int i=tail;i>=2;i--)
	{
		for(int j=1;j<=n;j++)
		{
			if(!stick[j].vis)
			{
				if(stick[j].l==queue[i-1]&&stick[j].r==queue[i])
				{
					stick[j].vis=true;
					cout<<j<<" -"<<endl;
					break;
				}
				if(stick[j].r==queue[i-1]&&stick[j].l==queue[i])
				{
					stick[j].vis=true;
					cout<<j<<" +"<<endl;
					break;
				}
			}	
		}
	}
	return 0;
}
bool check(int p)
{
	for(int i=0;i<=6;i++)
	{
		if(point[p].next[i])
		{
			return false;
		}
	}
	return true;
}
void dfs(int p)
{
	point[p].vis=true;
	for(int i=0;i<=6;i++)
	{
		while(point[p].next[i])
		{
			point[p].next[i]--;
			int next_point=i;
			point[next_point].next[p]--;
			dfs(next_point);
		}
	}
	if(check(p))
	{
		tail++;
		queue[tail]=p;
	}
	return;
}