hdu 2874 Connections between cities 带权lca判是否联通
Connections between cities
Time Limit: 10000/5000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Now, your task comes. After giving you the condition of the roads, we want to know if there exists a path between any two cities. If the answer is yes, output the shortest path between them.
1 3 2
2 4 3
5 2 3
1 4
4 5
6
Hint
Huge input, scanf recommended.
#include<iostream>
#include<cstdio>
#include<cmath>
#include<string>
#include<queue>
#include<algorithm>
#include<stack>
#include<cstring>
#include<vector>
#include<list>
#include<set>
#include<map>
#define true ture
#define false flase
using namespace std;
#define ll long long
#define inf 0xfffffff
int scan()
{
int res = , ch ;
while( !( ( ch = getchar() ) >= '' && ch <= '' ) )
{
if( ch == EOF ) return << ;
}
res = ch - '' ;
while( ( ch = getchar() ) >= '' && ch <= '' )
res = res * + ( ch - '' ) ;
return res ;
}
#define maxn 100010
#define M 22
int father[maxn];
struct is
{
int v,next,w;
} edge[maxn*];
int deep[maxn],jiedge;
int dis[maxn];
int head[maxn];
int fa[maxn][M];
int findd(int x)
{
return x==father[x]?x:father[x]=findd(father[x]);
}
int hebing(int u,int v)
{
int x=findd(u);
int y=findd(v);
if(x!=y)
father[x]=y;
}
void add(int u,int v,int w)
{
jiedge++;
edge[jiedge].v=v;
edge[jiedge].w=w;
edge[jiedge].next=head[u];
head[u]=jiedge;
}
void dfs(int u)
{
for(int i=head[u]; i; i=edge[i].next)
{
int v=edge[i].v;
int w=edge[i].w;
if(!deep[v])
{
dis[v]=dis[u]+edge[i].w;
deep[v]=deep[u]+;
fa[v][]=u;
dfs(v);
}
}
}
void st(int n)
{
for(int j=; j<M; j++)
for(int i=; i<=n; i++)
fa[i][j]=fa[fa[i][j-]][j-];
}
int LCA(int u , int v)
{
if(deep[u] < deep[v]) swap(u , v) ;
int d = deep[u] - deep[v] ;
int i ;
for(i = ; i < M ; i ++)
{
if( ( << i) & d ) // 注意此处,动手模拟一下,就会明白的
{
u = fa[u][i] ;
}
}
if(u == v) return u ;
for(i = M - ; i >= ; i --)
{
if(fa[u][i] != fa[v][i])
{
u = fa[u][i] ;
v = fa[v][i] ;
}
}
u = fa[u][] ;
return u ;
}
void init(int n)
{
for(int i=;i<=n;i++)
father[i]=i;
memset(head,,sizeof(head));
memset(fa,,sizeof(fa));
memset(deep,,sizeof(deep));
jiedge=;
}
int main()
{
int x,n,t;
while(~scanf("%d%d%d",&n,&x,&t))
{
init(n);
for(int i=; i<x; i++)
{
int u,v,w;
scanf("%d%d%d",&u,&v,&w);
add(u,v,w);
add(v,u,w);
hebing(u,v);
}
for(int i=;i<=n;i++)
if(!deep[i])
{
deep[i]=;
dis[i]=;
dfs(i);
}
st(n);
while(t--)
{
int a,b;
scanf("%d%d",&a,&b);
if(findd(a)!=findd(b))
printf("Not connected\n");
else
printf("%d\n",dis[a]-*dis[LCA(a,b)]+dis[b]);
}
}
return ;
}
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