51nod 最长递增子序列

nlogn版最长递增子序列。线段树。（其实常数蛮大的。。。。）

#include<iostream>
#include<cstring>
#include<algorithm>
#define maxn 50050
using namespace std;
int n,ls[maxn<<],rs[maxn<<],val[maxn<<],root,tot=;
struct pnt
{
    int id,val;
}p[maxn];
bool cmp(pnt x,pnt y)
{
    if (x.val!=y.val) return x.val<y.val;
    return x.id>y.id;
}
void addpnt(int id,int val)
{
    p[id].id=id;
    p[id].val=val;
}
void build(int &now,int left,int right)
{
    now=++tot;val[now]=;
    if (left==right) return;
    int mid=(left+right)>>;
    build(ls[now],left,mid);
    build(rs[now],mid+,right);
}
void pushup(int now)
{
    val[now]=max(val[ls[now]],val[rs[now]]);
}
int ask(int now,int left,int right,int l,int r)
{
    if ((left==l) && (right==r))
        return val[now];
    int mid=(left+right)>>;
    if (r<=mid) return ask(ls[now],left,mid,l,r);
    else if (l>=mid+) return ask(rs[now],mid+,right,l,r);
    else return max(ask(ls[now],left,mid,l,mid),ask(rs[now],mid+,right,mid+,r));
}
void modify(int now,int left,int right,int pos,int x)
{
    if ((left==right) && (left==pos))
    {
        val[now]=x;
        return;
    }
    int mid=(left+right)>>;
    if (pos<=mid) modify(ls[now],left,mid,pos,x);
    else modify(rs[now],mid+,right,pos,x);
    pushup(now);
}
int main()
{
    scanf("%d",&n);
    build(root,,n);
    for (int i=;i<=n;i++)
    {
        int x;
        scanf("%d",&x);
        addpnt(i,x);
    }
    sort(p+,p+n+,cmp);
    for (int i=;i<=n;i++)
    {
        int regis;
        if (p[i].id==) regis=;
        else regis=ask(root,,n,,p[i].id-);
        modify(root,,n,p[i].id,regis+);
    }
    printf("%d\n",val[]);
    return ;
}