BZOJ1131: [POI2008]Sta

  1 #include<cstdio>
  2 
  3 #include<cstdlib>
  4 
  5 #include<cmath>
  6 
  7 #include<cstring>
  8 
  9 #include<algorithm>
 10 
 11 #include<iostream>
 12 
 13 #include<vector>
 14 
 15 #include<map>
 16 
 17 #include<set>
 18 
 19 #include<queue>
 20 
 21 #include<string>
 22 
 23 #define inf 1000000000
 24 
 25 #define maxn 1000000+1000
 26 
 27 #define maxm 500+100
 28 
 29 #define eps 1e-10
 30 
 31 #define ll long long
 32 
 33 #define pa pair<int,int>
 34 
 35 #define for0(i,n) for(int i=0;i<=(n);i++)
 36 
 37 #define for1(i,n) for(int i=1;i<=(n);i++)
 38 
 39 #define for2(i,x,y) for(int i=(x);i<=(y);i++)
 40 
 41 using namespace std;
 42 
 43 inline int read()
 44 
 45 {
 46 
 47     int x=0,f=1;char ch=getchar();
 48 
 49     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
 50 
 51     while(ch>=‘0‘&&ch<=‘9‘){x=10*x+ch-‘0‘;ch=getchar();}
 52 
 53     return x*f;
 54 
 55 }
 56 int n,tot,head[maxn],dep[maxn];
 57 ll s[maxn],sum[maxn];
 58 struct edge{int go,next;}e[2*maxn];
 59 inline void insert(int x,int y){e[++tot].go=y;e[tot].next=head[x];head[x]=tot;}
 60 inline void dfs(int x)
 61 {
 62     s[x]=1;
 63     for(int i=head[x],y;i;i=e[i].next)
 64      if(!dep[y=e[i].go])
 65      {
 66          sum[y]=dep[y]=dep[x]+1;
 67          dfs(y);
 68          s[x]+=s[y];
 69          sum[x]+=sum[y];
 70      }
 71 }     
 72 inline void dfs2(int x)
 73 {
 74     for(int i=head[x],y;i;i=e[i].next)
 75     if(dep[y=e[i].go]>dep[x])
 76     {
 77         sum[y]=sum[x]-s[y]+n-s[y];
 78         dfs2(y);
 79     }
 80 }
 81 
 82 int main()
 83 
 84 {
 85 
 86     freopen("input.txt","r",stdin);
 87 
 88     freopen("output.txt","w",stdout);
 89 
 90     n=read();
 91     for1(i,n-1){int x=read(),y=read();insert(x,y);insert(y,x);};
 92     dep[1]=sum[1]=1;
 93     dfs(1);
 94     dfs2(1);
 95     int ans=0;
 96     for1(i,n)if(sum[i]>sum[ans])ans=i;
 97     printf("%d\n",ans);    
 98 
 99     return 0;
100 
101 }