bzoj2125 最短路

  1 //It is made by wfj_2048~
  2 #include <algorithm>
  3 #include <iostream>
  4 #include <complex>
  5 #include <cstring>
  6 #include <cstdlib>
  7 #include <cstdio>
  8 #include <vector>
  9 #include <cmath>
 10 #include <queue>
 11 #include <stack>
 12 #include <map>
 13 #include <set>
 14 #define inf (1<<30)
 15 #define N (40010)
 16 #define il inline
 17 #define RG register
 18 #define ll long long
 19 #define File(s) freopen(s".in","r",stdin),freopen(s".out","w",stdout)
 20 
 21 using namespace std;
 22 
 23 int n,m,q;
 24 
 25 struct edge{ int nt,to,dis; };
 26 
 27 struct YFtree{
 28     
 29     edge g[2*N]; int head[N],top[N],fa[N],son[N],dep[N],tid[N],pos[N],sz[N],dis[N],D[N],fg[N],nn,num,cnt;
 30     
 31     il void insert(RG int from,RG int to,RG int dis){
 32     g[++num]=(edge){head[from],to,dis},head[from]=num; swap(from,to);
 33     g[++num]=(edge){head[from],to,dis},head[from]=num; return;
 34     }
 35     
 36     il void dfs1(RG int x,RG int p){
 37     fa[x]=p,dep[x]=dep[p]+1,sz[x]=1; RG int v;
 38     for (RG int i=head[x];i;i=g[i].nt){
 39         v=g[i].to; if (v==p) continue;
 40         dis[v]=dis[x]+g[i].dis;
 41         dfs1(v,x),sz[x]+=sz[v];
 42         if (sz[son[x]]<=sz[v]) son[x]=v;
 43     }
 44     return;
 45     }
 46     
 47     il void dfs2(RG int x,RG int p,RG int anc){
 48     top[x]=anc,tid[x]=++cnt,pos[cnt]=x;
 49     if (son[x]) dfs2(son[x],x,anc); RG int v;
 50     for (RG int i=head[x];i;i=g[i].nt){
 51         v=g[i].to; if (v==p || v==son[x]) continue;
 52         dfs2(v,x,v);
 53     }
 54     return;
 55     }
 56     
 57     il int lca(RG int u,RG int v){
 58     while (top[u]!=top[v]){
 59         if (dep[top[u]]<dep[top[v]]) swap(u,v);
 60         u=fa[top[u]];
 61     }
 62     return dep[u]<dep[v] ? u : v;
 63     }
 64 
 65     il int jump(RG int u,RG int Lca){
 66     RG int last;
 67     while (top[u]!=top[Lca])
 68         last=top[u],u=fa[top[u]];
 69     return u==Lca ? last : pos[tid[Lca]+1];
 70     }
 71     
 72     il int query(RG int u,RG int v){
 73     RG int Lca=lca(u,v);
 74     if (Lca<=n) return dis[u]+dis[v]-2*dis[Lca];
 75     RG int uu=jump(u,Lca),vv=jump(v,Lca);
 76     RG int du=dis[uu]-dis[Lca],dv=dis[vv]-dis[Lca];
 77     if (!fg[uu]) du=D[Lca]-du; if (!fg[vv]) dv=D[Lca]-dv;
 78     if (du>dv) swap(du,dv);
 79     return dis[u]-dis[uu]+dis[v]-dis[vv]+min(dv-du,D[Lca]-(dv-du));
 80     }
 81     
 82 }YF;
 83 
 84 struct Graph{
 85     
 86     edge g[2*N]; int head[N],fa[N],dep[N],dis[N],dfn[N],low[N],st[N],num,cnt;
 87     
 88     il void insert(RG int from,RG int to,RG int dis){
 89     g[++num]=(edge){head[from],to,dis},head[from]=num; return;
 90     }
 91     
 92     il void dfs(RG int x,RG int p){
 93     fa[x]=p,dep[x]=dep[p]+1,dfn[x]=low[x]=++cnt; RG int v;
 94     for (RG int i=head[x];i;i=g[i].nt){
 95         v=g[i].to; if (v==p) continue;
 96         if (!dfn[v]){
 97         dis[v]=dis[x]+g[i].dis,dfs(v,x);
 98         low[x]=min(low[x],low[v]);
 99         } else low[x]=min(low[x],dfn[v]);
100         if (dfn[x]<low[v]) YF.insert(x,v,g[i].dis);
101     }
102     for (RG int i=head[x];i;i=g[i].nt){
103         v=g[i].to; if (v==p) continue;
104         if (fa[v]!=x && dfn[x]<dfn[v]) build(x,v,g[i].dis);
105     }
106     return;
107     }
108     
109     il void build(RG int rt,RG int x,RG int d){
110     RG int top=dep[x]-dep[rt]+1,tot=d,Dis=0;
111     for (RG int i=x;i!=rt;i=fa[i])
112         st[top--]=i,tot+=dis[i]-dis[fa[i]];
113     YF.D[++YF.nn]=tot,st[1]=rt,top=dep[x]-dep[rt]+1;
114     for (RG int i=1;i<=top;++i){
115         RG int dd=min(Dis,tot-Dis);
116         YF.fg[st[i]]=dd==Dis;
117         YF.insert(YF.nn,st[i],dd);
118         Dis+=dis[st[i+1]]-dis[st[i]];
119     }
120     return;
121     }
122     
123 }G;
124 
125 il int gi(){
126     RG int x=0,q=1; RG char ch=getchar();
127     while ((ch<‘0‘ || ch>‘9‘) && ch!=‘-‘) ch=getchar();
128     if (ch==‘-‘) q=-1,ch=getchar();
129     while (ch>=‘0‘ && ch<=‘9‘) x=x*10+ch-48,ch=getchar(); return q*x;
130 }
131 
132 il void work(){
133     n=gi(),m=gi(),q=gi(); YF.nn=n;
134     for (RG int i=1,u,v,w;i<=m;++i){
135     u=gi(),v=gi(),w=gi();
136     G.insert(u,v,w),G.insert(v,u,w);
137     }
138     G.dfs(1,0); YF.dfs1(1,0); YF.dfs2(1,0,1);
139     for (RG int i=1,u,v;i<=q;++i){
140     u=gi(),v=gi();
141     printf("%d\n",YF.query(u,v));
142     }
143     return;
144 }
145 
146 int main(){
147     File("shortest");
148     work();
149     return 0;
150 }