bzoj 1669: [Usaco2006 Oct] Hungry Cows Hungry Cows [dp+tree array+hash]

Longest ascending subsequence. Although the data can be directly n-squared, another nlogn
transfer is written: f[i]=max(f[j]+1)(a[j]<a[i])
O(n^2)

#include<iostream>
#include<cstdio>
using namespace std;
const int N=5005;
int n,a[N],f[N],ans;
int read()
{
    int r=0,f=1;
    char p=getchar();
    while(p>'9'||p<'0')
    {
        if(p=='-')
            f=-1;
        p=getchar();
    }
    while(p>='0'&&p<='9')
    {
        r=r*10+p-48;
        p=getchar();
    }
    return r*f;
}
int main()
{
    n=read();
    for(int i=1;i<=n;i++)
        a[i]=read();
    for(int i=1;i<=n;i++)
    {
        for(int j=0;j<i;j++)
            if(a[j]<a[i]&&f[j]+1>f[i])
                f[i]=f[j]+1;
        ans=max(ans,f[i]);
    }
    printf("%d\n",ans);
    return 0;
}

O(nlogn) tree array + hash

#include<iostream>
#include<cstdio>
#include<map>
#include<algorithm>
using namespace std;
const int N=5005;
int n,a[N],f[N],ans,g[N],t[N];
map<int,int>mp;
int read()
{
    int r=0,f=1;
    char p=getchar();
    while(p>'9'||p<'0')
    {
        if(p=='-')
            f=-1;
        p=getchar();
    }
    while(p>='0'&&p<='9')
    {
        r=r*10+p-48;
        p=getchar();
    }
    return r*f;
}
inline int lb(int x)
{
    return x&(-x);
}
void update(int x,int v)
{
    for(int i=x;i<=n;i+=lb(i))
        t[i]=max(t[i],v);
}
int ques(int x)
{
    int re=0;
    for(int i=x;i>=1;i-=lb(i))
        re=max(re,t[i]);
    return re;
}
int main()
{
    n=read();
    for(int i=1;i<=n;i++)
        a[i]=g[i]=read();
    sort(g+1,g+1+n);
    for(int i=1;i<=n;i++)
        mp[g[i]]=i;
    for(int i=1;i<=n;i++)
        a[i]=mp[a[i]];
    for(int i=1;i<=n;i++)
    {
        f[i]=ques(a[i]-1)+1;
        update(a[i],f[i]);
        ans=max(ans,f[i]);
    }
    printf("%d\n",ans);
    return 0;
}