CSES – Salary Queries

#include<bits/stdc++.h>
#define pii pair<int,int>
#define f first
#define s second
#define fastio ios_base::sync_with_stdio(0);cin.tie(0)
using namespace std;
//declare
#include<ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using ordered_set = tree<pii,null_type,less<pii>,rb_tree_tag,tree_order_statistics_node_update>;
const int maxn = 2e5+5;
int n,q,salary[maxn],timer;
ordered_set st;
//
signed main(){
    fastio;
    cin>>n>>q;
    for(int i=1;i<=n;i++){
        int x; cin>>x;
        salary[i] = x;
        st.insert({x,timer++});
    }
    while(q--){
        char op; cin>>op;
        int a,b; cin>>a>>b;
        if(op == '!'){
            pii p = {salary[a],0};
            st.erase(st.find_by_order(st.order_of_key(p)));
            salary[a] = b;
            st.insert({b,timer++});
        }
        else{
            pii p = {b+1,0}, q = {a,0};
            cout<<st.order_of_key(p)-st.order_of_key(q)<<"\n";
        }
    }
    return 0;
}