思路:主席樹查詢區間<=x的和
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <set>
#include<iostream>
#include<vector>
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define SIS std::ios::sync_with_stdio(false)
#define space putchar(' ')
#define enter putchar('\n')
#define lson root<<1
#define rson root<<1|1
typedef pair<int,int> PII;
const int mod=1e4+7;
const int N=2e5+10;
const int inf=0x7f7f7f7f;
ll gcd(ll a,ll b)
{
return b==0?a:gcd(b,a%b);
}
ll lcm(ll a,ll b)
{
return a*(b/gcd(a,b));
}
template <class T>
void read(T &x)
{
char c;
bool op = 0;
while(c = getchar(), c < '0' || c > '9')
if(c == '-')
op = 1;
x = c - '0';
while(c = getchar(), c >= '0' && c <= '9')
x = x * 10 + c - '0';
if(op)
x = -x;
}
template <class T>
void write(T x)
{
if(x < 0)
x = -x, putchar('-');
if(x >= 10)
write(x / 10);
putchar('0' + x % 10);
}
int n,m,cnt,root[N],a[N],x,y,k;
struct node
{
int l,r,sum;
}T[N*50];
void update(int l,int r,int &x,int y,int pos)
{
T[++cnt]=T[y];
T[cnt].sum++,x=cnt;
if(l==r)return ;
int mid=l+r>>1;
if(mid>=pos)update(l,mid,T[x].l,T[y].l,pos);
else update(mid+1,r,T[x].r,T[y].r,pos);
}
int query(int l,int r,int x,int y,int lk,int rk)
{
if(r<=rk)return T[y].sum-T[x].sum;
int mid=(l+r)/2;
if(rk<=mid)return query(l,mid,T[x].l,T[y].l,lk,rk);
else if(lk>mid) return query(mid+1,r,T[x].r,T[y].r,lk,rk);
else return query(l,mid,T[x].l,T[y].l,lk,mid)+query(mid+1,r,T[x].r,T[y].r,mid+1,k);
}
int main()
{
SIS;
cin>>n>>m;
for(int i=1;i<=n;i++)
{
cin>>a[i];
}
for(int i=1;i<=n;i++)
{
update(1,n,root[i],root[i-1],a[i]);
}
while(m--)
{
cin>>x>>y>>k;
int ans=query(1,n,root[x-1],root[y],1,k);
cout<<ans<<endl;
}
return 0;
}