poj 3378 Crazy Thairs dp

#include <iostream>
#include <cstdio>
#include <cstring>
#include <set>
typedef unsigned long long ll;
using namespace std;
const int maxn=5e4+9;
ll tree[6][maxn],dp[maxn][6];
int a[maxn];
int n;

typedef struct node
{
    int data,id;
    bool operator <(const node &xx) const
    {
        if(data==xx.data)
        return(id<xx.id);
        return(data<xx.data);
    }
};

int lowbit(int x)
{
    return(x&-x);
}

void insert(int x,int t,ll tmp)
{
    for(int i=x;i<=n;i+=lowbit(i))
    tree[t][i]+=tmp;
}

ll getsum(int x,int t)
{
    ll ans=0;
    for(int i=x;i>=1;i-=lowbit(i))
    ans+=tree[t][i];
    return(ans);
}

int main()
{
    set <node> d;
//    freopen("in.txt","r",stdin);
    while(scanf("%d",&n)!=EOF)
    {
        d.clear();
        for(int i=1;i<=n;i++)
        {
            scanf("%d",&a[i]);
            node x;
            x.data=a[i];
            x.id=i;
            d.insert(x);
        }
        int k=0,tmp;
        for(set <node>::iterator i=d.begin();i!=d.end();i++)
        {
            if(i==d.begin()||i->data!=tmp) k++;
            a[i->id]=k;
            tmp=i->data;
        }

        memset(dp,0,sizeof(dp));
        memset(tree,0,sizeof(tree));
        for(int i=1;i<=n;i++)
        {
            dp[i][1]=1;
            insert(a[i],1,dp[i][1]);
            for(int j=1;j<=4;j++)
            {
                dp[i][j+1]=getsum(a[i]-1,j);
                insert(a[i],j+1,dp[i][j+1]);
            }
        }
        ll ans=0,ans1=0;
        for(int i=1;i<=n;i++)
        {
            ans+=dp[i][5];
            ans1+=ans/ll(1000000000000000);
            ans%=1000000000000000;
        }
        if(ans1)
        {
            printf("%lld",ans1);
            printf("%015lld
",ans);
        }
        else
        printf("%lld
",ans);
    }
    return 0;
}