1820

/*
LCA问题，离线tarjan算法
*/

// include file
#include 
#include 
#include 
#include 
#include 
#include 

#include 
#include 
#include 
#include 
#include 
#include 

#include 
#include 
#include 
#include 
#include 
#include 
#include 

using namespace std;

// typedef
typedef long long LL;
typedef unsigned long long ULL;

// 
#define read freopen("in.txt","r",stdin)
#define write freopen("out.txt","w",stdout)
#define FORi(a,b,c) for(int i=(a);i<(b);i+=c)
#define FORj(a,b,c) for(int j=(a);j<(b);j+=c)
#define FORk(a,b,c) for(int k=(a);k<(b);k+=c)
#define FORp(a,b,c) for(int p=(a);p<(b);p+=c)

#define FF(i,a)    for(int i=0;i<(a);i+++)
#define FFD(i,a)   for(int i=(a)-1;i>=0;i--)
#define Z(a) (a<<1)
#define Y(a) (a>>1)

const double eps = 1e-6;
const double INFf = 1e10;
const int INFi = 1000000000;
const double Pi = acos(-1.0);

template inline T sqr(T a){return a*a;}
template inline T TMAX(T x,T y)
{
	if(x>y) return x;
	return y;
}
template inline T TMIN(T x,T y)
{
	if(x inline void SWAP(T &x,T &y)
{
	T t = x;
	x = y;
	y = t;
}
template inline T MMAX(T x,T y,T z)
{
	return TMAX(TMAX(x,y),z);
}


// code begin
int T,N,Q;
#define MAXN 10010
#define MAXQ 20010

struct node1
{
	int next;
	int t;
	int w;
};
node1 mem1[MAXN*2];
int G[MAXN];
int dx1;

struct node2
{
	int next;
	int t;
	int i;
};
node2 mem2[MAXQ*2];
int Q2[MAXQ];
int dx2;

int dst[MAXN];
bool used[MAXN];
int ans[MAXQ];

//
int father[MAXN];

void Add_edge(int a,int b,int c)
{
	mem1[dx1].t = b;
	mem1[dx1].w = c;
	mem1[dx1].next = G[a];
	G[a] = dx1++;
}

void Add_query(int a,int b,int i)
{
	mem2[dx2].t = b;
	mem2[dx2].i = i;
	mem2[dx2].next = Q2[a];
	Q2[a] = dx2++;
}

int Find(int i)
{
	if(father[i]!=i) 
		father[i] = Find(father[i]);
	return father[i];
}

// 合并需注意，必须a是b的father
void Joint(int a,int b)
{
	a = Find(a);
	b = Find(b);
	father[b] = a;
}

void LCA_Tarjan(int i)
{
	used[i] = true;
	father[i] = i;
	int mdx = G[i];
	while(mdx!=-1)
	{
		int v = mem1[mdx].t;
		if(!used[v])
		{
			dst[v] = dst[i] + mem1[mdx].w;
			LCA_Tarjan(v);
			Joint(i,v);
		}

		mdx = mem1[mdx].next;
	}

	mdx = Q2[i];
	while(mdx!=-1)
	{
		int v = mem2[mdx].t;
		if(used[v])
		{
			ans[ mem2[mdx].i ] = dst[i]+dst[v]-2*dst[Find(v)];
		}
		mdx = mem2[mdx].next;
	}
}

int main()
{
	read;
	write;
	int a,b,c;
	scanf("%d",&T);
	while(T--)
	{
		scanf("%d %d",&N,&Q);
		memset(G,-1,sizeof(G));
		dx1 = 0;
		FORi(0,N-1,1)
		{
			scanf("%d %d %d",&a,&b,&c);
			Add_edge(a,b,c);
			Add_edge(b,a,c);
		}

		memset(Q2,-1,sizeof(Q2));
		dx2 = 0;
		FORi(0,Q,1)
		{
			scanf("%d %d",&a,&b);
			Add_query(a,b,i);
			Add_query(b,a,i);
		}

		//
		memset(used,0,sizeof(used));
		memset(dst,0,sizeof(dst));
		FORi(1,N+1,1)
		{
			if(!used[i])
			{
				LCA_Tarjan(i);
			}
		}
		
		FORi(0,Q,1)
		{
			printf("%d\n",ans[i]);
		}
		printf("\n");
	}
	return 0;
}

转载于:https://www.cnblogs.com/ac2012/archive/2011/03/28/1997795.html