luogu1966 火柴排队(离散化+树状数组)

 1 #include<bits/stdc++.h>
 2 #define pa pair<int,int>
 3 #define ll long long
 4 using namespace std;
 5 const int maxn=100010,mod=99999997;
 6 
 7 inline ll rd(){
 8     ll x=0;char c=getchar();int neg=1;
 9     while(c<‘0‘||c>‘9‘){if(c==‘-‘) neg=-1;c=getchar();}
10     while(c>=‘0‘&&c<=‘9‘) x=x*10+c-‘0‘,c=getchar();
11     return x*neg;
12 }
13 
14 int N;
15 pa h1[maxn],h2[maxn];
16 int nh[maxn],rank[maxn];
17 int tr[maxn];
18 
19 inline int lowbit(int x){return x&(-x);}
20 
21 inline void add(int x,int y){
22     for(;x<=N;x+=lowbit(x)) tr[x]=(tr[x]+y)%mod;
23 }
24 inline int query(int x){
25     int re=0;for(;x;x-=lowbit(x)) re=(re+tr[x])%mod;return re;
26 }
27 
28 int main(){
29     int i,j,k;
30     N=rd();
31     for(i=1;i<=N;i++) h1[i]=make_pair(rd(),i);
32     for(i=1;i<=N;i++) h2[i]=make_pair(rd(),i);
33     sort(h1+1,h1+N+1);sort(h2+1,h2+N+1);
34     for(i=1;i<=N;i++){
35         rank[i]=h1[i].second;
36     }for(i=1;i<=N;i++){
37         nh[h2[i].second]=rank[i];
38     }int ans=0;
39     for(i=N;i;i--){
40         ans=(ans+query(nh[i]))%mod;
41         add(nh[i],1);
42     }printf("%d\n",ans);
43     return 0;
44 }