题目链接：http://www.lydsy.com/JudgeOnline/problem.php?id=3295
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${O(nlogn)}$
1 #include<iostream> 2 #include<ext/pb_ds/assoc_container.hpp> 3 #include<cstdio> 4 #include<algorithm> 5 #include<vector> 6 #include<cstdlib> 7 #include<cmath> 8 #include<cstring> 9 #include<set> 10 using namespace std; 11 using namespace __gnu_pbds; 12 #define maxn 1001000 13 #define llg long long 14 #define yyj(a) freopen(a".in","r",stdin),freopen(a".out","w",stdout); 15 llg n,m,d[maxn],ans,wz[maxn],v; 16 tree<llg,null_type,less<llg>,rb_tree_tag,tree_order_statistics_node_update>c[maxn]; 17 18 //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) 19 llg cc[maxn]; 20 inline llg lowbit(llg x){return x&-x;} 21 22 void add(llg x,llg val) {while (x<=n) {c[x].insert(val);x+=lowbit(x);}} 23 24 void del(llg x,llg val) {while (x<=n) c[x].erase(val),x+=lowbit(x);} 25 26 void add_(llg x,llg val) {while (x<=n) cc[x]+=val,x+=lowbit(x);} 27 28 llg sum_(llg x) {llg tot=0; while (x>0) tot+=cc[x],x-=lowbit(x); return tot;} 29 30 llg sum(llg x,llg val) 31 { 32 llg tot=0; 33 while (x>0) 34 { 35 tot+=c[x].size(); 36 llg xiao=c[x].order_of_key(val+1); 37 tot-=xiao; 38 x-=lowbit(x); 39 }return tot; 40 } 41 42 llg summ(llg x,llg val) 43 { 44 llg tot=0; 45 while (x>0) 46 { 47 tot+=c[x].order_of_key(val+1); 48 x-=lowbit(x); 49 } 50 return tot; 51 } 52 53 void init() 54 { 55 cin>>n>>m; 56 for (llg i=1;i<=n;i++) 57 { 58 scanf("%lld",&d[i]); 59 wz[d[i]]=i; 60 ans+=sum_(n)-sum_(d[i]); 61 add_(d[i],1); 62 add(i,d[i]); 63 } 64 65 } 66 67 void work() 68 { 69 llg x,da,xiao; 70 while (m--) 71 { 72 printf("%lld ",ans); 73 scanf("%lld",&v); 74 x=wz[v]; 75 da=sum(x,v); 76 xiao=summ(n,v)-summ(x,v); 77 ans-=da+xiao; 78 del(x,v); 79 } 80 } 81 82 int main() 83 { 84 yyj("bzoj3295"); 85 init(); 86 work(); 87 return 0; 88 }