hdu2876 Connections between cities

图不一定联通，所以用并查集找各个联通块的祖先分别建图，之后就和LCA的步骤差不多了

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<algorithm>
#include<vector>
using namespace std;
inline int read(){
	int sum=0,x=1;
	char ch=getchar();
	while(ch<'0'||ch>'9'){
		if(ch=='-')
			x=0;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9')
		sum=(sum<<1)+(sum<<3)+(ch^48),ch=getchar();
	return x?sum:-sum;;
}
inline void write(int x){
	if(x<0)
		putchar('-'),x=-x;
	if(x>9)
		write(x/10);
	putchar(x%10+'0');
}
const int M=1e4+4;
const int maxlog=14;
struct node{
	int v,nextt,w;
}e[M<<2];
int head[M],deep[M],grand[M][maxlog],dis[M][maxlog],f[M],s,n,tot,root,sign;
void addedge(int u,int v,int w){
	e[tot].v=v;
	e[tot].w=w;
	e[tot].nextt=head[u];
	head[u]=tot++;
}
int find(int x){
	return x==f[x]?x:f[x]=find(f[x]);
}
void dfs(int x){
	for(int i=1;i<=s;i++){
		grand[x][i]=grand[grand[x][i-1]][i-1];
		dis[x][i]=dis[x][i-1]+dis[grand[x][i-1]][i-1];
		if(!grand[x][i])
			break;
	}
	for(int i=head[x];~i;i=e[i].nextt){
		int v=e[i].v;
	//	cout<<"exit"<<endl;
		if(v!=grand[x][0]){
			grand[v][0]=x;
			deep[v]=deep[x]+1;
			dis[v][0]=e[i].w;
			dfs(v);
		}
	}
}
void init(){
	s=floor(log(n+0.0)/log(2.0));
	deep[0]=-1;
	dfs(root);
}
int LCA(int a,int b){
	if(deep[a]>deep[b])
		swap(a,b);
	int ans=0;
	for(int i=s;i>=0;i--)
		if(deep[a]<deep[b]&&deep[a]<=deep[grand[b][i]])
			ans+=dis[b][i],b=grand[b][i];
	for(int i=s;i>=0;i--)
		if(grand[a][i]!=grand[b][i])
			ans+=dis[a][i],a=grand[a][i],ans+=dis[b][i],b=grand[b][i];
	if(a!=b)
		ans+=dis[a][0],ans+=dis[b][0];
	return ans;
}
int main(){
	int m,k;
	while(~scanf("%d%d%d",&n,&m,&k)){
		for(int i=0;i<=n;i++)
			f[i]=i,head[i]=-1,deep[i]=0;
		memset(grand,0,sizeof(grand));
		memset(dis,0,sizeof(dis));
		tot=0;
		while(m--){
			int x=read(),y=read(),w=read();
			addedge(x,y,w);
			addedge(y,x,w);
			int p=find(x);
			int q=find(y);
			if(p!=q)
				f[q]=p;
		}
		for(int i=1;i<=n;i++){
			if(f[i]==i){
				root=i;
				init();
			}
		//	cout<<"!!!"<<f[i]<<endl;
		}
	/*	for(int i=1;i<=n;i++)
			cout<<deep[i]<<" ";
		cout<<endl;*/
		while(k--){
			int u=read(),v=read();
			int x=find(u);
			int y=find(v);
			if(x==y){
				write(LCA(u,v));
				putchar('\n');
			}
			else
				puts("Not connected");
		}
	}
	return 0;
}

标签：cities,int,ch,grand,Connections,hdu2876,ans,include,dis
来源： https://www.cnblogs.com/starve/p/10809112.html