Lol no one's updated the website in months. Was I right it was I right?

No one's gonna make additions. Instead submit a pull request and pray it gets review on the next year

Hi! It's actually mentioned in the article here. But I generally agree that the code with 0-based Fenwick is pretty ugly + makes our life harder e.g. when we want to treat all segments uniformly but we can't because of the lacks of the value for the zero-length prefix. That being said, feel free to make a pull request, I think overall it would be a welcomed addition.

#include
#include

class FenwickTree {
private:
std::vector tree;
int size;

public:
// Constructor to initialize the Fenwick Tree with the given size
FenwickTree(int n) {
size = n;
tree.resize(n + 1, 0); // 1-based indexing, so we allocate n + 1
}

// Update the value at index `index` by `value`
void update(int index, int value) {
    for (; index <= size; index += index & -index) {
        tree[index] += value;
    }
}

// Query the prefix sum from 1 to `index`
int query(int index) const {
    int sum = 0;
    for (; index > 0; index -= index & -index) {
        sum += tree[index];
    }
    return sum;
}

// Query the sum in the range [left, right]
int rangeQuery(int left, int right) const {
    return query(right) - query(left - 1);
}

};

int main() {
int n = 10; // Size of the Fenwick Tree
FenwickTree fenwick(n);

// Example updates
fenwick.update(1, 5);   // Add 5 at index 1
fenwick.update(2, 3);   // Add 3 at index 2
fenwick.update(3, 7);   // Add 7 at index 3

// Query the sum from 1 to 3
std::cout << "Sum from 1 to 3: " << fenwick.query(3) << std::endl; // Output: 15

// Query the sum in range [2, 3]
std::cout << "Sum from 2 to 3: " << fenwick.rangeQuery(2, 3) << std::endl; // Output: 10

return 0;

}

@UtsavKashyap1710 thanks for the code, but issues section is only for text discussions, actual contribuitions should be done via pull requests.

Also take a note of #1298, which addresses a similar concern.