bzoj1046[HAOI2007]上升序列

Posted 2020-07-02 YJY_

首先求出以每个数为开头上升序列长度，即倒着做最长下降子序列

然后，把字典序尽量小的放前面

即若要求的序列长度为x，如果以第一个数（字典序最小的数）开头的最长上升子序列大等于x，则将它放在答案第一个，第二个数开头小于x，则舍弃，第三个大于x-1，放答案第二个，以此类推

 

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cstring>

#include<cstdio>

#include<cmath>

using namespace std;

 

typedef long long LL;

 

#ifdef WIN32

#define orz "%lld"

#else

#define orz "%I64d"

#endif

 

#define MAXN 10010

int f[MAXN],a[MAXN],b[MAXN];

int n,m;

int ans;

int x;

 

void work(int x)

{

    int res=0;

    for (int i=1;i<=n;i++)

        if (f[i]>=x && a[i]>res)

        {

            printf("%d",a[i]);

            if (x!=1)

                printf(" ");

            res=a[i];

            x--;

            if (!x)

                break;

        }

    printf("\n");

}

 

int find(int x)

{

    int l=1,r=ans,tmp=0;

    while (l<=r)

    {

        int m=(l+r)>>1;

        if (b[m]>x)

            tmp=m,l=m+1;

        else

            r=m-1;

    }

    return tmp;

}

 

void get()

{

    for (int i=n;i;i--)

    {

        int t=find(a[i]);

        f[i]=t+1;

        ans=max(ans,t+1);

        //b[t+1]=min(b[t+1],a[i]);

        if(b[t+1]<a[i])

            b[t+1]=a[i];

    }

}

 

int main()

{

    scanf("%d",&n);

    for (int i=1;i<=n;i++)

        scanf("%d",&a[i]);

    get();

    scanf("%d",&m);

    while (m--)

    {

        scanf("%d",&x);

        if (x<=ans)

            work(x);

        else

            printf("Impossible\n");

    }   

    return 0;

}