[cogs731] [网络流24题#6] 最长递增子序列 [网络流，最大流]

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <queue>
#include <stack>
#include <vector>

using namespace std;

#define    Debug

template<const int _n,const int _m>
struct Edge
{
    struct Edge_base { int    to,next,w; }e[_m]; int    cnt,p[_n];
    Edge() { clear(); }
    void    insert(const int x,const int y,const int z)
    { e[++cnt].to=y; e[cnt].next=p[x]; e[cnt].w=z; p[x]=cnt; return ; }
    int    start(const int x) { return p[x]; }
    void    clear() { cnt=1,memset(p,0,sizeof(p)); }
    Edge_base&    operator[](const int x) { return e[x]; }
};

Edge<11000,1100000>    e;
int    Ans=0,tAns;
int    n,a[5100],cur[11000],level[11000],SSS,TTT;
int    f[11000];

bool    Bfs(const int S)
{
    int    i,t;
    queue<int>    Q;
    memset(level,0,sizeof(level));
    level[S]=1;
    Q.push(S);
    while(!Q.empty())
    {
        t=Q.front(),Q.pop();
        for(i=e.start(t);i;i=e[i].next)
        {
            if(!level[e[i].to] && e[i].w)
            {
                level[e[i].to]=level[t]+1;
                Q.push(e[i].to);
            }
        }
    }
    return level[TTT];
}

int    Dfs(const int S,const int bk)
{
    if(S==TTT)return bk;
    int    rest=bk;
    for(int &i=cur[S];i;i=e[i].next)
    {
        if(level[e[i].to]==level[S]+1 && e[i].w)
        {
            int    flow=Dfs(e[i].to,min(rest,e[i].w));
            e[i].w-=flow;
            e[i^1].w+=flow;
            if((rest-=flow)<=0)break;
        }
    }
    if(rest==bk)level[S]=0;
    return bk-rest;
}

int    Dinic()
{
    int    flow=0;
    while(Bfs(SSS))
    {
        memcpy(cur,e.p,sizeof(cur));
        flow+=Dfs(SSS,0x3f3f3f3f);
    }
    return flow;
}

void    Calc1()
{
    int    i,j;

    for(i=1;i<=n;++i)
    {
        if(f[i]==1)e.insert(SSS,i,1),e.insert(i,SSS,0);
        if(f[i]==Ans)e.insert(i+n,TTT,1),e.insert(TTT,i+n,0);
        e.insert(i,i+n,1);
        e.insert(i+n,i,0);
    }
    for(i=1;i<=n;++i)
    {
        for(j=i+1;j<=n;++j)
        {
            if(a[j]>=a[i] && f[j]==f[i]+1)
                e.insert(i+n,j,1),e.insert(j,i+n,0);
        }
    }
    printf("%d\n",tAns=Dinic());
}

void    Calc2()
{
    int    i,j;
    e.clear();
    for(i=1;i<=n;++i)
    {
        int    v=1;
        if(i==1 || i==n)v=0x3f3f3f3f;
        if(f[i]==1)e.insert(SSS,i,v),e.insert(i,SSS,0);
        if(f[i]==Ans)e.insert(i+n,TTT,v),e.insert(TTT,i+n,0);
        e.insert(i,i+n,v);
        e.insert(i+n,i,0);
    }
    for(i=1;i<=n;++i)
    {
        for(j=i+1;j<=n;++j)
        {
            if(a[j]>=a[i] && f[j]==f[i]+1)
                e.insert(i+n,j,1),e.insert(j,i+n,0);
        }
    }
    int    temp=Dinic();
    if(temp>=0x3f3f3f3f)temp=tAns;
    printf("%d\n",temp);
    return ;
}


int main()
{
    freopen("alis.in","r",stdin);
    freopen("alis.out","w",stdout);

    int    i,j;

    scanf("%d",&n);
    for(i=1;i<=n;++i)scanf("%d",&a[i]);

    for(i=1;i<=n;++i)
    {
        f[i]=1;
        for(j=1;j<i;++j)
            if(a[j]<=a[i])f[i]=max(f[i],f[j]+1);
        Ans=max(Ans,f[i]);
    }

    printf("%d\n",Ans);

    SSS=n<<1|1,TTT=SSS+1;
    Calc1();
    Calc2();

    return 0;
}