I am trying to solve this problem: https://cses.fi/problemset/task/1648/ using Binary Indexed Tree. My solution does not work, but I think it is correct.
Heres is my code:
#include <bits/stdc++.h>
using namespace std;
const long MAXN = 2e5+5;
long n, q, arr[MAXN];
long long bit[MAXN];
void update(long x, long y) {
for (; x <= n; x += x&-x) bit[x] += y;
}
long long query(long x) {
long long sum = 0;
for (; x > 0; x -= x&-x) sum += bit[x];
return sum;
}
long long sum(long l, long r) { return query(r) - query(l-1); }
int main() {
ios::sync_with_stdio(false); cin.tie(0);
cin >> n >> q;
for (long i = 1; i <= n; i++) {
cin >> arr[i];
update(i, arr[i]);
}
while (q--) {
long i, a, b;
cin >> i >> a >> b;
if (i == 1) update(a, b-bit[a]);
else cout << sum(a, b) << "\n";
}
return 0;
}
Thanks for your time!!!