1987.txt

北大ACM题目例程 详细的解答过程 程序实现 算法分析

#include"stdio.h"
#include"algorithm"
using namespace std;

long  use[16];
long  father[40010];
long  queue[40010];
long  lchild[40010][16];
long  rchild[40010][16];
long  sum[40010][16];
long  depth[40010][16];

long  value[40010],dist[40010];
long  m,n,k,kind,answer;

long findit(long key,long s1,long deep)
{ 
	long &lc=lchild[s1][deep],&rc=rchild[s1][deep],sumnow=sum[s1][deep];
	long now=depth[s1][deep];

	if(now==key)
	{
		if(rc>=0)return sumnow-sum[rc][deep+1];
		else return sumnow;
	}

	else if(key<now)
	{
		if(lc>=0)return findit(key,lc,deep+1);
		return 0;
	}
	else 
	{
		if(rc>=0)return sumnow-sum[rc][deep+1]+findit(key,rc,deep+1);
		return sumnow;
	}
}

void merge(long s1,long s2,long deep)
{ 
	long &lc=lchild[s1][deep],&rc=rchild[s1][deep];
	long &lc2=lchild[s2][deep],&rc2=rchild[s2][deep];

	sum[s1][deep]+=sum[s2][deep];
			
	if(lc<0)lc=lc2;
	else 
	{
		if(lc2>=0)merge(lc,lc2,deep+1);
	}
	
	if(rc<0)rc=rc2;
	else 
	{
		if(rc2>=0)merge(rc,rc2,deep+1);
	}
}

void great(long key)
{
	long down=0,up=kind-1,deep=0,c,*p=0;
	while(1)
	{
		c=(down+up)/2;
		depth[use[deep]][deep]=value[c];
		sum[use[deep]][deep]=1;
		if(p)*p=use[deep];
		use[deep]++;
				
		if(value[c]==key)break;
		else if(key<value[c]){up=c-1;p=&lchild[use[deep]-1][deep];}
		else {down=c+1;p=&rchild[use[deep]-1][deep];}
		deep++;
	}
}

////////////////////////////////////////////////////////
struct edge
{
	long from,to;
	long distance;
}e[40020*2];

long begin[40020],end[40020];


int cmp(edge a,edge b)
{
	return a.from<b.from||(a.from==b.from&&a.to<b.to);
}

void init()
{
	scanf("%ld %ld",&n,&m);

	long i,j;char c;

	for(i=0;i<2*m;i+=2)
	{
		scanf("%ld %ld %ld %c",&e[i].from,&e[i].to,&e[i].distance,&c);

		e[i].from--;
		e[i].to--;

		e[i+1].from=e[i].to;
		e[i+1].to=e[i].from;
		e[i+1].distance=e[i].distance;
	}

	sort(&e[0],&e[m*2],cmp);
	
	begin[0]=0;
	for(i=1;i<m*2;i++)
	{
		if(e[i].from!=e[i-1].from)
		{
			end[e[i-1].from]=i;
			begin[e[i].from]=i;
		}
	}
	end[n-1]=2*m;
	scanf("%ld",&k);
	
	for(i=0;i<16;i++)
	{
		use[i]=0;
		for(j=0;j<n;j++)
		{
			rchild[j][i]=lchild[j][i]=-1;
			sum[j][i]=0;
		}
	}
	long now,qh=0,qt=1;
	dist[0]=0;queue[0]=0;father[0]=-1;

	while(qh<qt)
	{
		now=queue[qh++];
		for(i=begin[now];i<end[now];i++)
		if((j=e[i].to)!=father[now])
		{
			queue[qt++]=j;
			father[j]=now;
			dist[j]=dist[now]+e[i].distance;
		}
	}
	
	copy(dist,dist+n,value);
	sort(value,value+n);
	
	for(i=1,kind=1;i<n;i++)
	if(value[i]!=value[i-1])value[kind++]=value[i];	

	answer=0;
	return;
}

void countit(long t,long s,int deep,long l)
{
	long a=sum[s][deep],lc=lchild[s][deep],rc=rchild[s][deep];
		
	if(lc>=0)
	{
		a-=sum[lc][deep+1];
		countit(t,lc,deep+1,l);
	}
	
	if(rc>=0)
	{
		a-=sum[rc][deep+1];
		countit(t,rc,deep+1,l);
	}
	
	if(a>0)
	{
		answer+=a*findit(k+l-depth[s][deep],t,0);
	}
	
	return;

}

void doit()
{
	long s,f,i,l,tree[40010];
	
	for(i=0;i<n;i++)
	{
		tree[i]=i;
		great(dist[i]);
	}
	for(i=n-1;i>0;i--)
	{   
		s=queue[i];
		f=father[s];
		l=dist[f]*2;
		if(sum[tree[s]][0]<sum[tree[f]][0])
		{
			countit(tree[f],tree[s],0,l);
			merge(tree[f],tree[s],0);
		}
		else
		{	
			countit(tree[s],tree[f],0,l);
			merge(tree[s],tree[f],0);
			tree[f]=tree[s];
		}
	}
	
	printf("%ld\n",answer);
	return ;
}

int main()
{
	init();
	doit();
	return 0;
}