LCA最近公共祖先题集

tarjan详解：https://user.qzone.qq.com/50222268/blog/1504145322

注意：离线存储用vector存

1，题目:http://codevs.cn/problem/2370/

#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>

using namespace std;

struct node
{
	int y,wei;
};

struct node1
{
	int y,ans;
};

const int maxSize=75000;
vector <node> N[maxSize+5];
vector <node1> M[maxSize+5];
int n,m;
int ans[maxSize+5],vis[maxSize+5],visit[maxSize+5],fa[maxSize+5],dis[maxSize+5];

int find(int x)
{
	int r=x,temp;
	
	while (fa[r]!=r)
	{
		r=fa[r];
	}
	while (fa[x]!=r)
	{
		temp=fa[x];
		fa[x]=r;
		x=temp;
	}
	return r;
}

void dfs1(int x)
{
	int i;
	node n1;
	
	for (i=0;i<N[x].size();i++)
	{
		n1=N[x][i];
		if (vis[n1.y]==1)
			continue;
		vis[n1.y]=1;
			
		dis[n1.y]=dis[x]+n1.wei;
		dfs1(n1.y);
		vis[n1.y]=0;
	}
}

void dfs(int x)
{
	int i,zx;
	node n1;
	node1 n2;
	
	for (i=0;i<N[x].size();i++)
	{
		n1=N[x][i];
		if (vis[n1.y]==1)
			continue;
		vis[n1.y]=1;
		dfs(n1.y);
		vis[n1.y]=0;
		fa[n1.y]=x;
	}
	for (i=0;i<M[x].size();i++)
	{
		n2=M[x][i];
		if (visit[n2.y]==0)
			continue;
		zx=find(n2.y);
		ans[n2.ans]=dis[x]-dis[zx]+dis[n2.y]-dis[zx];
	}
	visit[x]=1;
}


int main()
{
	int i,x,y,z;
	node n1;
	node1 n2;
	
	freopen("a.txt","r",stdin);
	scanf("%d",&n);
	
	for (i=1;i<n;i++)
	{
		scanf("%d%d%d",&x,&y,&z);
		n1.y=y;	n1.wei=z;
		N[x].push_back(n1);
		n1.y=x;
		N[y].push_back(n1);
	}
	scanf("%d",&m);
	for (i=0;i<m;i++)
	{
		scanf("%d%d",&x,&y);
		n2.y=y;	n2.ans=i;
		M[x].push_back(n2);
		n2.y=x;
		M[y].push_back(n2);
	}
	memset(vis,0,sizeof(vis));
	memset(visit,0,sizeof(visit));
	memset(dis,0,sizeof(dis));
	for (i=0;i<n;i++)
		fa[i]=i;
		
	vis[0]=1;
	dfs1(0);
	dfs(0);
	for (i=0;i<m;i++)
		printf("%d\n",ans[i]);
	
	return 0;
}

2，题目：http://codevs.cn/problem/1036/

#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>

using namespace std;

struct node
{
	int y,ans;
};

const int maxSize=30000;
vector <node> M[maxSize+5];
vector <int> N[maxSize+5];
int n,m;
int ans[maxSize+5],fa[maxSize+5],vis[maxSize+5],visit[maxSize+5],dis[maxSize+5];

void dfs1(int x)
{
	int i,y;
	
	for (i=0;i<N[x].size();i++)
	{
		y=N[x][i];
		if (vis[y]==1)
			continue;
		vis[y]=1;
		dis[y]=dis[x]+1;
		dfs1(y);
		vis[y]=0;
	}
}

int find(int x)
{
	int r=x,temp;
	
	while (r!=fa[r])
		r=fa[r];
	while (fa[x]!=r)
	{
		temp=fa[x];
		fa[x]=r;
		x=temp;
	}
	return r;
}

void dfs(int x)
{
	int i,y,zx;
	node n1;
	
	for (i=0;i<N[x].size();i++)
	{
		y=N[x][i];
		if (vis[y]==1)
			continue;
		vis[y]=1;
		dfs(y);
		vis[y]=0;
		fa[y]=x;
	}
	for (i=0;i<M[x].size();i++)
	{
		n1=M[x][i];
		if (visit[n1.y]==0)
			continue;
		zx=find(n1.y);
		ans[n1.ans]=dis[x]-dis[zx]+dis[n1.y]-dis[zx];
	}
	visit[x]=1;
}

int main()
{
	int i,x,y,ans1;
	node n1;
	
	freopen("a.txt","r",stdin);
	scanf("%d",&n);
	for (i=1;i<n;i++)
	{
		scanf("%d%d",&x,&y);
		N[x].push_back(y);
		N[y].push_back(x);
	}
	scanf("%d",&m);
	scanf("%d",&x);
	for (i=1;i<m;i++)
	{
		scanf("%d",&y);
		n1.y=y;	n1.ans=i;
		M[x].push_back(n1);
		n1.y=x;
		M[y].push_back(n1);
		x=y;
	}
	memset(vis,0,sizeof(vis));
	memset(visit,0,sizeof(visit));
	memset(dis,0,sizeof(dis));
	for (i=1;i<=n;i++)
		fa[i]=i;
	vis[1]=1;
	dfs1(1);
	dfs(1);
	ans1=0;
	for (i=1;i<m;i++)
		ans1+=ans[i];
	printf("%d\n",ans1);
	
	return 0;
}