[树状数组][2019徐州网络赛I]query

题目链接：https://nanti.jisuanke.com/t/41391

思路：nlogn找出所有合法(i,j)，二维偏序查询

AC代码：

#include<bits/stdc++.h>
#define lowbit(x) x&(-x)
typedef long long ll;
using namespace std;

ll n,m;
ll a[100005],pos[100005];
ll c[100005];
vector<ll> v[100005];
struct Query{
  ll l,r;
}q[100005];
struct Node{
  ll x,y;
  bool operator<(const Node& b)const{
    if(x==b.x) return y<b.y;
    return x<b.x;
  }
}node[100005*4];
map<pair<ll,ll>,ll> sum;

void add(ll x,ll val){
    for(ll i=x;i<=n;i+=lowbit(i)){
        c[i]+=val;
    }
}

ll getsum(ll x){
    ll ret=0;
    for(ll i=x;i>0;i-=lowbit(i)){
        ret+=c[i];
    }
    return ret;
}

int main()
{
    scanf("%lld%lld",&n,&m);
    for(ll i=1;i<=n;i++) scanf("%lld",&a[i]),pos[a[i]]=i;

    for(ll i=1;i<=n;i++){
        for(ll j=a[i]*2;j<=n;j+=a[i]){
            if(pos[j]>i) v[i].push_back(pos[j]);
        }
    }

    for(ll i=1;i<=n;i++){
        for(ll j=a[i]*2;j<=n;j+=a[i]){
            if(pos[j]<i) v[i].push_back(pos[j]);
        }
    }

    ll cnt=0;
    for(ll i=1;i<=m;i++) {
        scanf("%lld%lld",&q[i].l,&q[i].r);
        node[++cnt]=Node{q[i].r,q[i].r};
        node[++cnt]=Node{q[i].l-1,q[i].l-1};
        node[++cnt]=Node{q[i].l-1,q[i].r};
        node[++cnt]=Node{q[i].r,q[i].l-1};
    }
    sort(node+1,node+1+cnt);

    ll l=1;
    for(ll i=1;i<=cnt;i++){
        while(l<=node[i].x){
            for(auto j:v[l]) add(j,1);
            l++;
        }
        sum[make_pair(node[i].x,node[i].y)]=getsum(node[i].y);
    }

    for(ll i=1;i<=m;i++){
        ll ans=sum[make_pair(q[i].r,q[i].r)]-sum[make_pair(q[i].l-1,q[i].r)]-sum[make_pair(q[i].r,q[i].l-1)]+sum[make_pair(q[i].l-1,q[i].l-1)];
        printf("%lld
",ans);
    }
    return 0;
}