Method buildTree

Java/Range-Sum-Query-Mutable.java:28–33

(int[] nums)

    // build the segment tree and store it in array of size 2 * nums[] length
    // so the nums[] values are stores at leaves of the segment tree.
    private void buildTree(int[] nums) {
        for (int i = n, j = 0; i < 2 * n; i++, j++)
            tree[i] = nums[j];
        for (int i = n - 1; i > 0; --i)
            tree[i] = tree[i * 2] + tree[i * 2 + 1];
    }

    // 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) {