【BZOJ】3295: [Cqoi2011]动态逆序对

题目链接：http://www.lydsy.com/JudgeOnline/problem.php?id=3295

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mamaya,弱鸡xrdog终于会写树套树啦....

将树状数组中每一个节点看成一棵平衡树，支持$RANK$操作，每次删除一个数之前，支持查询位置在当前数之前权值比他大的有多少个，查询位置在当前数之后权值比他小的有多少个，再支持删除操作。

复杂度${O(nlogn^{2})}$,空间复杂度${O(nlogn)}$

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 #include<iostream>
 #include<ext/pb_ds/assoc_container.hpp>
 #include<cstdio>
 #include<algorithm>
 #include<vector>
 #include<cstdlib>
 #include<cmath>
 #include<cstring>
 #include<set>
 using namespace std;
 using namespace __gnu_pbds;
 #define maxn 1001000
 #define llg long long
 #define yyj(a) freopen(a".in","r",stdin),freopen(a".out","w",stdout);
 llg n,m,d[maxn],ans,wz[maxn],v;
 tree<llg,null_type,less<llg>,rb_tree_tag,tree_order_statistics_node_update>c[maxn];  

 //tree<llg,null_mapped_type,less<llg>,rb_tree_tag,tree_order_statistics_node_update>c[maxn];  //-----如果您的编译器版本较低(BZOJ)
 llg cc[maxn];
 inline llg lowbit(llg x){return x&-x;}

 void add(llg x,llg val)  {while (x<=n) {c[x].insert(val);x+=lowbit(x);}}

 void del(llg x,llg val)  {while (x<=n) c[x].erase(val),x+=lowbit(x);}

 void add_(llg x,llg val) {while (x<=n) cc[x]+=val,x+=lowbit(x);}

 llg sum_(llg x) {llg tot=; while (x>) tot+=cc[x],x-=lowbit(x); return tot;}

 llg sum(llg x,llg val)
 {
     llg tot=;
     while (x>)
     {
         tot+=c[x].size();
         llg xiao=c[x].order_of_key(val+);
         tot-=xiao;
         x-=lowbit(x);
 }return tot;
 }

 llg summ(llg x,llg val)
 {
     llg tot=;
     while (x>)
     {
         tot+=c[x].order_of_key(val+);
         x-=lowbit(x);
     }
     return tot;
 }

 void init()
 {
     cin>>n>>m;
     for (llg i=;i<=n;i++)
     {
         scanf("%lld",&d[i]);
         wz[d[i]]=i;
         ans+=sum_(n)-sum_(d[i]);
         add_(d[i],);
         add(i,d[i]);
     }

 }

 void work()
 {
     llg x,da,xiao;
     while (m--)
     {
         printf("%lld\n",ans);
         scanf("%lld",&v);
         x=wz[v];
         da=sum(x,v);
         xiao=summ(n,v)-summ(x,v);
         ans-=da+xiao;
         del(x,v);
     }
 }

 int main()
 {
     yyj("bzoj3295");
     init();
     work();
     return ;
 }