loj#2391 「JOISC 2017 Day 1」港口设施

分析

https://yhx-12243.github.io/OI-transit/records/uoj356%3Bloj2391%3Bac2534.html

代码

#include<bits/stdc++.h>
using namespace std;
const int mod = 1e9+;
vector<int>v[];
int fa[][],a[],b[],bel[],is[],n,m,vis[];
inline int sf(int wh,int x){return fa[wh][x]==x?x:fa[wh][x]=sf(wh,fa[wh][x]);}
inline void dfs(int x,int f,int d){
    if(vis[x]!=-){
      if(vis[x]!=d){
          puts("");
          exit();
      }
      return;
    }
    vis[x]=d;
    for(int i=;i<v[x].size();i++)
      if(v[x][i]!=f)dfs(v[x][i],x,d^);
}
int main(){
    int i,j,k,Ans=;
    scanf("%d",&n);
    for(i=;i<=*n+;i++)fa[][i]=fa[][i]=i;
    for(i=;i<=n;i++){
      scanf("%d%d",&a[i],&b[i]);
      bel[a[i]]=bel[b[i]]=i;
      is[b[i]]=;
      fa[][b[i]]=b[i]+;
    }
    for(i=;i<=*n;i++)
      if(is[i]){
          int x=a[bel[i]],la=;
          for(j=sf(,x+);j<=i;j=sf(,j+)){
            j=sf(,j);
            v[bel[j]].push_back(bel[i]);
            v[bel[i]].push_back(bel[j]);
            if(la)fa[][la]=j;
            la=j;
        }
        fa[][x]=x+;
      }
    memset(vis,-,sizeof(vis));
    for(i=;i<=n;i++)
      if(vis[i]==-)Ans=Ans*%mod,dfs(i,,);
    cout<<Ans;
    return ;
}