三人三鬼过河(野人与传教士过河)问题c/c++代码

Posted 2021-08-30 辉小歌

#include<bits/stdc++.h>
using namespace std;
vector< pair<int,int> > path;
map< vector<int> ,int > vis;
void dfs(int La,int Lb,int Ra,int Rb,int flag)// La 左边的好人数  Lb左边的坏人数  flag是左边操作还是右边
{
	if( (Lb>La&&La) || (Rb>Ra&&Ra) )
	{
		return;
	} 
	if( (La+Lb) ==6)
	{
		for(int i=0;i<path.size();i++)
		{
			if(i%2==0) cout<<"右->左"<<" ";
			else cout<<"左->右"<<" ";
			cout<<path[i].first<<" "<<path[i].second<<endl;
		}
		cout<<endl;
		return;
	}
	if(flag)//左边到右边
	{
		if(Ra>0) //一个好人
		{
			vector<int> s;
			s.push_back(Ra-1),s.push_back(Rb),s.push_back(0);//0代表左
			if(!vis[s]) 
			{
				path.push_back({1,0});
				vis[s]=1;
				dfs(La+1,Lb,Ra-1,Rb,0);
				path.pop_back();
			}
		}
		if(Ra>=2)//两个好人
		{
			vector<int> s;
			s.push_back(Ra-2),s.push_back(Rb),s.push_back(0);
			if(!vis[s]) 
			{
				path.push_back({1,1});
				vis[s]=1;
				dfs(La+2,Lb,Ra-2,Rb,0);
				path.pop_back();
			}
		}
		if(Rb>0) //一个坏人
		{
			vector<int> s;
			s.push_back(Ra),s.push_back(Rb-1),s.push_back(0);
			if(!vis[s]) 
			{
				path.push_back({-1,0});
				vis[s]=1;
				dfs(La,Lb+1,Ra,Rb-1,0);
				path.pop_back();
			}
		}
		if(Rb>=2)//两个坏人
		{
			vector<int> s;
			s.push_back(Ra),s.push_back(Rb-2),s.push_back(0);
			if(!vis[s]) 
			{
				path.push_back({-1,-1});
				vis[s]=1;
				dfs(La,Lb+2,Ra,Rb-2,0);
				path.pop_back();
			}
		}
		if(Ra&&Rb)//一个好人一个坏人
		{
			vector<int> s;
			s.push_back(Ra-1),s.push_back(Rb-1),s.push_back(0);
			if(!vis[s]) 
			{
				path.push_back({1,-1});
				vis[s]=1;
				dfs(La+1,Lb+1,Ra-1,Rb-1,0);
				path.pop_back();
			}
		}
	}
	else
	{
		if(La>0) 
		{
			vector<int> s;
			s.push_back(La-1),s.push_back(Lb),s.push_back(1);
			if(!vis[s])
			{
				path.push_back({1,0});
				vis[s]=1;
				dfs(La-1,Lb,Ra+1,Rb,1);
				path.pop_back();
			}	
		}
		if(La>=2)
		{
			vector<int> s;
			s.push_back(La-2),s.push_back(Lb),s.push_back(1);
			if(!vis[s])
			{
				path.push_back({1,1});
				vis[s]=1;
				dfs(La-2,Lb,Ra+2,Rb,1);
				path.pop_back();
			}
		}
		if(Lb>0) 
		{
			vector<int> s;
			s.push_back(La),s.push_back(Lb-1),s.push_back(1);
			if(!vis[s]) 
			{
				path.push_back({-1,0});
				vis[s]=1;
				dfs(La,Lb-1,Ra,Rb+1,1);
				path.pop_back();
			}
		}
		if(Lb>=2)
		{
			vector<int> s;
			s.push_back(La),s.push_back(Lb-2),s.push_back(1);
			if(!vis[s]) 
			{
				path.push_back({-1,-1});
				vis[s]=1;
				dfs(La,Lb-2,Ra,Rb+2,1);
				path.pop_back();
			}
		}
		if(La&&Lb)
		{
			vector<int> s;
			s.push_back(La-1),s.push_back(Lb-1),s.push_back(1);
			if(!vis[s]) 
			{
				path.push_back({1,-1});
				vis[s]=1;
				dfs(La-1,Lb-1,Ra+1,Rb+1,1);
				path.pop_back();
			}
		}
	}
}
int main(void)
{
	dfs(0,0,3,3,1);
	return 0;
}