mirror of
https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
187 lines
4.6 KiB
C++
187 lines
4.6 KiB
C++
#pragma comment(linker, "/STACK:102400000,102400000")
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#include <algorithm>
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#include <iostream>
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#include <cstdio>
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#include <cstring>
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#include <vector>
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#include <stack>
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using namespace std;
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const int N=200005;
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#define Log 22
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struct Edge
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{
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int v;
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Edge *nxt;
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}memo[N*10],*cur,*h_bef[N],*h_aft[N];
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void addEdge(int u,int v,Edge* head[])
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{
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cur->v=v; cur->nxt=head[u];
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head[u]=cur++;
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}
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int bnum,bn[N];
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vector<int> block[N];
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bool iscut[N];
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bool vis[N];
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stack<int> stk;
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int dfn[N],low[N],son_root,idx;
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int lab[N],id[N],son[N],fa[N];
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int dp[N][Log],dep[N];
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void tarjan(int pt_u,int pt_pre)
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{
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stack<int> stk_tar;
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stk_tar.push(pt_u); fa[pt_u]=pt_pre;
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while(stk_tar.size())
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{
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int u=stk_tar.top();
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int pre=fa[u];
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if(dfn[u]==0) dfn[u]=low[u]=++idx,stk.push(u);
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Edge* it;
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for(it=h_bef[u];it;it=it->nxt)
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{
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int v=it->v;
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if(v==pre) continue;
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if(fa[v]==-1)
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{
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fa[v]=u; stk_tar.push(v);
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h_bef[u]=it;
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break;
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}
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else
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{
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if(fa[v]==u)
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{
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low[u]=min(low[u],low[v]);
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if(dfn[u]<=low[v])
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{
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if(pre==-1) son_root++;
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else iscut[u]=1;
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while(1)
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{
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int top=stk.top(); stk.pop();
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block[bnum].push_back(top);
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if(top==v) break;
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}
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block[bnum].push_back(u);
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bnum++;
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}
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}
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else low[u]=min(low[u],dfn[v]);
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}
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}
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if(it==NULL) stk_tar.pop();
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}
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}
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void dfs(int u,int pre,int cnt,int iid)
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{
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dep[u]=dep[ dp[u][0] ]+1;
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for(int i=1;i<Log;i++) dp[u][i]= dp[ dp[u][i-1] ][ i-1 ];
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id[u]=iid; son[u]=cnt+bn[u];
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for(Edge* it=h_aft[u];it;it=it->nxt)
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{
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int v=it->v;
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if(v!=pre)
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{
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dp[v][0]=u;
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dfs(v,u,son[u],iid);
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}
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}
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}
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int lca(int u,int v)
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{
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if(dep[u]<dep[v]) swap(u,v);
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for(int st=(1<<(Log-1)),i=Log-1;i>=0;st>>=1,i--)
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{
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if(st<=dep[u]-dep[v])
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{
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u=dp[u][i];
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}
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}
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if(u==v) return u;
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for(int i=Log-1;i>=0;i--)
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{
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if(dp[u][i]!=dp[v][i])
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{
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u=dp[u][i];
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v=dp[v][i];
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}
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}
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return dp[u][0];
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}
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void init()
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{
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cur=memo;
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memset(h_bef,0,sizeof(h_bef));
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memset(h_aft,0,sizeof(h_aft));
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memset(dp,0,sizeof(dp));
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bnum=0; idx=0; son_root=0;
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while(stk.size()) stk.pop();
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for(int i=0;i<N;i++)
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{
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block[i].clear();
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dfn[i]=0; low[i]=0; lab[i]=-1;
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id[i]=i; iscut[i]=0; bn[i]=0;
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son[i]=0; dep[i]=0; vis[i]=0;
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fa[i]=-1;
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}
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}
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int main()
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{
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int n,m,Q,t_cnt=0;
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while(scanf("%d%d",&n,&m)!=EOF)
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{
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init();
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for(int i=0;i<m;i++)
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{
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int u,v; scanf("%d%d",&u,&v);
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addEdge(u,v,h_bef);
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addEdge(v,u,h_bef);
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}
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for(int i=0;i<n;i++) if(dfn[i]==0)
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{
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son_root=0;
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tarjan(i,-2);
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if(son_root>1) iscut[i]=1;
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}
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int k=0;
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for(int i=0;i<n;i++) if(iscut[i])
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{
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lab[i]=k; bn[k]=1; k++;
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}
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for(int i=0;i<bnum;i++)
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{
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for(int j=0;j<(int)block[i].size();j++)
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{
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int u=block[i][j];
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if(iscut[u])
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{
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addEdge(lab[u],k,h_aft);
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addEdge(k,lab[u],h_aft);
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}
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else lab[u]=k;
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}
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bn[k]=(int)block[i].size();
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k++;
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}
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for(int i=0;i<k;i++) if(dep[i]==0) dfs(i,-1,0,i);
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scanf("%d",&Q);
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printf("Case #%d:\n",++t_cnt);
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while(Q--)
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{
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int s,t; scanf("%d%d",&s,&t);
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if(s==t) printf("%d\n",n-1);
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else if(lab[s]==-1||lab[t]==-1||id[lab[s]]!=id[lab[t]]) printf("%d\n",n);
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else
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{
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s=lab[s]; t=lab[t];
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int parent=lca(s,t);
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int cnt=son[s]+son[t]-2*son[parent]+bn[parent];
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int len=dep[s]+dep[t]-2*dep[parent];
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int ans=cnt-len;
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printf("%d\n",n-ans);
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}
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}
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puts("");
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}
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return 0;
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}
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