Thank you nskybytskyi.

Starting in 15 minutes!

really excited!!!

thank you for putting in the effort to do such an amazing thing.

Can we please have more practice problems on segtrees? These are somewhat standard, lecture-style.

Hey guys, I have encountered a problem in cases problem Dynamic Sum Queries. My code fails for the second test case

Your code here...
#include <bits/stdc++.h>
using namespace std;

int n,q;
vector<long long> a(200005,0);
vector<long long> feenwick_tree(200005,0);

long long sum(int k){
    long long s=0;
    while(k>=1){
        s += feenwick_tree[k];
        k -= k&-k;
    }
    return s;
}

void add(int k, long long x){
    while(k<=n){
        feenwick_tree[k] += x;
        k += k&-k;
    }
}

int main(){
    cin>>n>>q;
    for(int i=1;i<=n;i++)
        cin>>a[i];
    for(int i=1;i<=n;i++){
        add(i,a[i]);
    }
    while(q-->0){
        long long q,i,j;
        cin>>q>>i>>j;
        if(q==1){
            j = j-a[i];
            add(i,j);
        }
        else{
            long long x1 = sum(j);
            long long x2 = sum(i-1);
            if(i==1)
                cout<<x1<<"\n";
            else
                cout<<x1-x2<<"\n";
        }
    }
    return 0;
}

Thank you, in advance.

Hey nskybytskyi can you please make a contest mashup or question list from easy to hard so that we can try and maybe later you can make a editorial video!