POJ-2299-Ultra-QuickSort（单点更新 + 区间查询+离散化）

#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
#include<queue>
#include<stack>
#include<set>
#include<vector>
#include<map>
const int maxn=5e5+5;
typedef long long ll;
using namespace std;
struct node
{
    ll l,r;
    ll sum;
}tree[maxn<<2];
int a[maxn],sub[maxn],cnt;

void pushup(int m)
{
    tree[m].sum=(tree[m<<1].sum+tree[m<<1|1].sum);
}
//void pushdown(int  m)
//{
//    if(tree[m].lazy)
//    {
//        tree[m<<1].lazy=tree[m].lazy;
//        tree[m<<1|1].lazy=tree[m].lazy;
//        tree[m<<1].sum=tree[m].lazy*(tree[m<<1].r-tree[m<<1].l+1);
//        tree[m<<1|1].sum=tree[m].lazy*(tree[m<<1|1].r-tree[m<<1|1].l+1);
//        tree[m].lazy=0; 
//    } 
//    return ;
//}
void build(int m,int l,int r)
{
    tree[m].l=l;
    tree[m].r=r;
    tree[m].sum=0;
    if(l==r)
    {
        tree[m].sum=0;
        return ;
    }
    int mid=(tree[m].l+tree[m].r)>>1;
    build(m<<1,l,mid);
    build(m<<1|1,mid+1,r);
    pushup(m);
    return ;
}
void update(int m,int index ,int  val)
{
    if(tree[m].l==index&&tree[m].l==tree[m].r)
    {
        tree[m].sum++;
        return ;
    }
    int mid=(tree[m].l+tree[m].r)>>1;
    if(index<=mid)
    {
        update(m<<1,index,val);
    }
    else 
    {
        update(m<<1|1,index,val);
    }
    pushup(m);
    return ; 
}
ll query(int m,int l,int r)
{
    if(l>r)
    {
        return 0;
    }
    if(tree[m].l==l&&tree[m].r==r)
    {
        return tree[m].sum;
    } 
//    pushdown(m);
    int mid=(tree[m].l+tree[m].r)>>1;
    if(r<=mid)
    {
        return query(m<<1,l,r);
    } 
    else if(l>mid)
    {
        return query(m<<1|1,l,r);
    }
    else
    {
        return query(m<<1,l,mid)+query(m<<1|1,mid+1,r);
    }
}

int main()
{ 
   int n;
   while(cin>>n)
   {
       if(n==0)
       {
           break;
    }
    for(int i=0;i<n;++i)scanf("%d",&sub[i]),a[i]=sub[i];
    sort(sub,sub+n);    
    int size=unique(sub,sub+n)-sub;   
    for(int i=0;i<n;i++)
    a[i]=lower_bound(sub,sub+size,a[i])-sub+1;
    build(1,1,size);
    ll sum=0;
    for(int t=0;t<n;t++)
    {
        sum+=query(1,a[t]+1,size);
        update(1,a[t],1);
    }
    printf("%lld\n",sum);
    
   }
   return 0;
}