BZOJ 1046 上升序列(LIS变形)

要保证长度为L的序列下标字典序最小，当然要尽量选前面的数。

如何判断前面的数是否满足条件？，只需要知道这个数开头的递增序列的最长长度是多少，如果不小于L，那么必然可以加入这个数。还需判断一下它是否大于前面的那个数就行了。

LIS用nlogn。

 

# include <cstdio>
# include <cstring>
# include <cstdlib>
# include <iostream>
# include <vector>
# include <queue>
# include <stack>
# include <map>
# include <set>
# include <cmath>
# include <algorithm>
using namespace std;
# define lowbit(x) ((x)&(-x))
# define pi acos(-1.0)
# define eps 1e-9
# define MOD 1000000007
# define INF 1000000000
# define mem(a,b) memset(a,b,sizeof(a))
# define FOR(i,a,n) for(int i=a; i<=n; ++i)
# define FO(i,a,n) for(int i=a; i<n; ++i)
# define bug puts("H");
# define lch p<<1,l,mid
# define rch p<<1|1,mid+1,r
# define mp make_pair
# define pb push_back
typedef pair<int,int> PII;
typedef vector<int> VI;
# pragma comment(linker, "/STACK:1024000000,1024000000")
typedef long long LL;
int Scan() {
    int res=0, flag=0;
    char ch;
    if((ch=getchar())=='-') flag=1;
    else if(ch>='0'&&ch<='9') res=ch-'0';
    while((ch=getchar())>='0'&&ch<='9')  res=res*10+(ch-'0');
    return flag?-res:res;
}
void Out(int a) {
    if(a<0) {putchar('-'); a=-a;}
    if(a>=10) Out(a/10);
    putchar(a%10+'0');
}
const int N=10005;
//Code begin...

int a[N], dp[N], len[N], num=0;

int bin_sea(int x)
{
    int l=1, r=num+1, mid;
    while (l<r) {
        mid=(l+r)>>1;
        if (len[mid]<=x) r=mid;
        else l=mid+1;
    }
    if (r==num+1) ++num;
    len[r]=x;
    return r;
}
int main ()
{
    int n, m, l, ma=0;
    scanf("%d",&n);
    FOR(i,1,n) scanf("%d",a+i);
    for (int i=n; i>=1; --i) dp[i]=bin_sea(a[i]), ma=max(ma,dp[i]);
    scanf("%d",&m);
    while (m--) {
        scanf("%d",&l);
        if (l>ma) {puts("Impossible"); continue;}
        int pre=0;
        FOR(i,1,n) {
            if (dp[i]>=l&&a[i]>pre) printf(l==1?"%d":"%d ",a[i]), --l, pre=a[i];
            if (!l) break;
        }
        putchar('\n');
    }
    return 0;
}