BZOJ 3289 Mato的文件管理（莫队+树状数组）

#include <cstdio>
#include <algorithm>
#include <cmath>
#include <cstring> 
const int N=50100;
using namespace std;
typedef long long LL;
int pos[N],a[N],disc[N],n,m,limit,i,l,r,c[N];
struct Q{
    int l,r,id; LL ans;
    friend bool operator < (const Q &a,const Q &b){
        return pos[a.l]<pos[b.l]||(pos[a.l]==pos[b.l]&&a.r<b.r);
    }
}ask[N];
bool cmp(const Q &a,const Q &b){return a.id<b.id;}
void read(int&a){
    char ch;while(!((ch=getchar())>=‘0‘)&&(ch<=‘9‘));
    a=ch-‘0‘;while(((ch=getchar())>=‘0‘)&&(ch<=‘9‘))a*=10,a+=ch-‘0‘;
}
void update(int x,int val){while(x<=n)c[x]+=val,x+=x&-x;}
LL query(int x){LL res=0;while(x)res+=c[x],x-=x&-x;return res;}
int main(){
    read(n);
    limit=(int)sqrt(n+0.5);
    for(i=1;i<=n;i++){read(a[i]);pos[i]=(i-1)/limit+1;}
    for(int i=1;i<=n;i++)disc[i]=a[i];
    sort(disc+1,disc+n+1);
    for(int i=1;i<=n;i++)a[i]=lower_bound(disc+1,disc+n+1,a[i])-disc;
    read(m); memset(c,0,sizeof(c));
    for(int i=1;i<=m;i++){read(ask[i].l);read(ask[i].r);ask[i].id=i;}
    sort(ask+1,ask+m+1); LL ans=0;
    for(int i=1,l=1,r=0;i<=m;i++){
        while(r<ask[i].r)r++,update(a[r],1),ans+=r-l+1-query(a[r]);  
        while(r>ask[i].r)update(a[r],-1),ans-=r-l-query(a[r]),r--;  
        while(l<ask[i].l)update(a[l],-1),ans-=query(a[l]-1),l++;  
        while(l>ask[i].l)l--,update(a[l],1),ans+=query(a[l]-1);
        ask[i].ans=ans;
    }sort(ask+1,ask+m+1,cmp);
    for(int i=1;i<=m;i++)printf("%lld\n",ask[i].ans);
    return 0;
}