POJ_Nearest Common Ancestors

最新推荐文章于 2019-03-01 16:50:52 发布

原创最新推荐文章于 2019-03-01 16:50:52 发布 · 420 阅读

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#include<iostream>  
#include<sstream>        
#include<string>        
#include<vector>        
#include<list>        
#include<set>        
#include<map>        
#include<stack>        
#include<queue>        
#include<algorithm>        
#include<cmath>        
#pragma warning(disable:4996)        
using namespace std;
class Tree
{
public:
	map<int, int>edge;
	Tree(const int &node_num)
	{
		for (int i = 0; i != node_num-1; i++)
		{
			int parent, child; cin >> parent >> child;			
			edge.insert(make_pair(child,parent));
		}
	}
	vector<int>getAncestor(const int &node)
	{
		vector<int>ancestor;
		for (int i = node;true;i=edge[i])
		{
			ancestor.push_back(i);
			if(edge.find(i)==edge.end())
			{
				break;
			}
		}	
		return ancestor;
	}
	int getLCA(const int &node1,const int &node2)
	{
		vector<int>ancestor1 = getAncestor(node1), ancestor2 = getAncestor(node2);
		for (size_t i = 0; i != ancestor1.size(); i++)
		{
			for (size_t j = 0; j != ancestor2.size(); j++)
			{
				if (ancestor1[i] == ancestor2[j])
				{
					return ancestor1[i];
				}
			}
		}
		return 0;
	}
};
int main()
{
	//freopen("input.txt", "r", stdin);  
	//freopen("output.txt", "w", stdout);  
	int T; cin >> T;
	while (T--)
	{
		int n; cin >> n;
		Tree tree(n);
		int node1, node2; cin >> node1 >> node2;
		cout << tree.getLCA(node1,node2) << endl;
	}
	return 0;
}

#include<iostream>  
#include<sstream>        
#include<string>        
#include<vector>        
#include<list>        
#include<set>        
#include<map>        
#include<stack>        
#include<queue>        
#include<algorithm>        
#include<cmath>        
#pragma warning(disable:4996)        
using namespace std;
class Tree
{
public:
	map<int, int>edge;
	vector<vector<int>>adjList;
	vector<int>depth;
	vector<int>isRoot;
	Tree(const int &node_num)
	{
		adjList.resize(node_num + 1);
		depth.resize(node_num + 1);
		isRoot.resize(node_num + 1,true);
		for (int i = 0; i != node_num-1; i++)
		{
			int parent, child; cin >> parent >> child;			
			edge.insert(make_pair(child,parent));
			adjList[parent].push_back(child);
			isRoot[child] = false;
		}
		for (int root = 1;true;root++)
		{
			if (isRoot[root])
			{
				depth[root] = 1;
				DFS(root, 2);
				break;
			}
		}
	}
	void DFS(int i,int curDepath)
	{
		for (size_t j = 0; j != adjList[i].size(); j++)
		{
			depth[adjList[i][j]] = curDepath;
			DFS(adjList[i][j], curDepath+1);
		}
	}
	vector<int>getAncestor(const int &node)
	{
		vector<int>ancestor;
		for (int i = node;true;i=edge[i])
		{
			ancestor.push_back(i);
			if(edge.find(i)==edge.end())
			{
				break;
			}
		}	
		return ancestor;
	}
	int getLCA(const int &node1,const int &node2)
	{
		int ancestor1 = node1, ancestor2 = node2;
		while (ancestor1 != ancestor2)
		{
			if (depth[ancestor1]<depth[ancestor2])
			{
				ancestor2 = edge[ancestor2];
			}
			else
			{
				ancestor1 = edge[ancestor1];
			}
		}
		return ancestor1;
	}
};
int main()
{
	//freopen("input.txt", "r", stdin);  
	//freopen("output.txt", "w", stdout);  
	int T; cin >> T;
	while (T--)
	{
		int n; cin >> n;
		Tree tree(n);
		int node1, node2; cin >> node1 >> node2;
		cout << tree.getLCA(node1,node2) << endl;
	}
	return 0;
}