private void modify(SegTreeNode root, int index, int value) {
if (root.start == index && root.end == index) {
root.count += value;
return;
}
int mid = root.start + (root.end - root.start) / 2;
if (root.start <= index && index <= mid) {
modify(root.left, index, value);
} else if (mid < index && index <= root.end) {
modify(root.right, index, value);
}
root.count = root.left.count + root.right.count;
}
private SegTreeNode build(int start, int end) {
if (end < start) {
return null;
}
SegTreeNode root = new SegTreeNode(start, end, 0);
int mid = start + (end - start) / 2;
if (start != end) {
root.left = build(start, mid);
root.right = build(mid + 1, end);
root.count = root.left.count + root.right.count;
} else {
root.count = 0;
}
return root;
}
