图论(无向图的割顶)：POJ 1144 Network

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
const int maxn=100010;
int n,fa[maxn],ch[maxn][2],sz[maxn];
int flip[maxn],pos[maxn],rt;
struct Node{
    int x,id;
}a[maxn];

void Flip(int x){
    swap(ch[x][0],ch[x][1]);
    flip[x]^=1;
}

void Push_down(int x){
    if(flip[x]){
        Flip(ch[x][0]);
        Flip(ch[x][1]);
        flip[x]=0;
    }
}

int pd[maxn];
void P(int x){
    int cnt=0;
    while(x){
        pd[++cnt]=x;
        x=fa[x];
    }
    while(cnt){
        Push_down(pd[cnt--]);
    }
}

void Push_up(int x){
    sz[x]=sz[ch[x][0]]+sz[ch[x][1]]+1;
}

void Rotate(int x){
    int y=fa[x],g=fa[y],c=ch[y][1]==x;
    ch[y][c]=ch[x][c^1];fa[ch[x][c^1]]=y;
    ch[x][c^1]=y;fa[y]=x;fa[x]=g;
    if(g)ch[g][ch[g][1]==y]=x;
    Push_up(y);
}

void Splay(int x,int g=0){
    P(x);
    for(int y;(y=fa[x])!=g;Rotate(x))
        if(fa[y]!=g)
            Rotate((ch[fa[y]][1]==y)==(ch[y][1]==x)?y:x);
    Push_up(x);        
    if(!g)rt=x;
}

int Build(int f,int l,int r){
    if(l>r)return 0;
    int mid=(l+r)>>1;fa[mid]=f;
    ch[mid][0]=Build(mid,l,mid-1);
    ch[mid][1]=Build(mid,mid+1,r);
    sz[mid]=1;
    Push_up(mid);
    return mid;
}

bool cmp(Node a,Node b){
    if(a.x!=b.x)
    return a.x<b.x;
    return a.id<b.id;
}

int main(){
    while(~scanf("%d",&n)&&n){
        memset(flip,0,sizeof(flip));
        rt=Build(0,1,n+2);
        for(int i=1;i<=n;i++)
            scanf("%d",&a[i].x);
        for(int i=1;i<=n;i++)
            a[i].id=i;    
        sort(a+1,a+n+1,cmp);
        for(int i=1;i<=n;i++)
            pos[i+1]=a[i].id+1;    
        pos[1]=1;pos[n+2]=n+2;
        for(int i=2,p;i<n+1;i++){
            Splay(pos[1]);
            Splay(pos[i],pos[1]);
            printf("%d ",sz[ch[ch[rt][1]][0]]+1);
            Splay(pos[i]);
            p=ch[pos[i]][1];
            while(ch[p][0]){
                Push_down(p);
                p=ch[p][0];
            }
            Push_down(p);
            Splay(pos[i-1]);
            Splay(p,pos[i-1]);
            Flip(ch[ch[rt][1]][0]);
        }
        printf("%d\n",n);
    }
    return 0;
}