Method update

Java/Range-Sum-Query-Mutable.java:36–51

(int pos, int val)

    // update the segment tree if new value to be inserted in tree, then update its parent at pos/2 and so on till root
    void update(int pos, int val) {
        pos += n;
        tree[pos] = val;
        while (pos > 0) {
            int left = pos;
            int right = pos;
            if (pos % 2 == 0) {
                right = pos + 1;
            } else {
                left = pos - 1;
            }
            // parent is updated after child is updated
            tree[pos / 2] = tree[left] + tree[right];
            pos /= 2;
        }
    }


    // this is responsible for the sum betweeen given ranges