hdu6047 Maximum Sequence【贪心+线段树】

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

using namespace std;
typedef long long LL;
typedef long long ll;
const int maxn = 5e5+100;
struct node
{
    int l,r;
    int maxx;
}tree[4*maxn];
int a[maxn],b[maxn];
void push_up(int i)
{
    tree[i].maxx = max(tree[i<<1].maxx,tree[i<<1|1].maxx);
}
void build(int i,int l,int r)
{
    tree[i].l = l,tree[i].r = r;
    tree[i].maxx = 0;
    if(l==r)
    {
        tree[i].maxx = a[l];
        return ;
    }
    int mid = (l+r)>>1;
    build(i<<1,l,mid);
    build(i<<1|1,mid+1,r);
    push_up(i);
}
void update(int i,int pos,int val)
{
    int l = tree[i].l;
    int r = tree[i].r;
    if(l==pos && r==pos)
    {
        tree[i].maxx = val;
        return ;
    }
    int mid = (l+r)>>1;
    if(mid>=pos)
        update(i<<1,pos,val);
    else
        update(i<<1|1,pos,val);
    push_up(i);
}
int query(int i,int l,int r)
{
    int L = tree[i].l;
    int R = tree[i].r;
    if(l<=L && R<=r)
        return tree[i].maxx;
    int mid = (L+R)>>1;
    int ans = 0;
    if(mid<r)
        ans = max(ans,query(i<<1|1,l,r));
    if(mid>=l)
        ans = max(ans,query(i<<1,l,r));
    return ans;
}
int main()
{
    int n;
    while(~scanf("%d",&n))
    {
        for(int i=1;i<=n;i++)
        {
            scanf("%d",&a[i]);
            a[i] -= i;
        }
        for(int i=1;i<=n;i++)
            scanf("%d",&b[i]);
        sort(b+1,b+n+1);
        build(1,1,2*n);
        ll ans = 0,r = n;
        for(int i = 1;i<=n;i++)
        {
            ll mm = query(1,b[i],r);
            r++;
            update(1,r,mm-r);
            ans = (ans+mm)%1000000007;
        }
        printf("%I64d\n",ans);
    }
    return 0;
}