您可以在每个节点中存储连接到左侧（小于）的叶子数，并在插入新叶子时增加在左侧传递的每个分支的计数。
通过将插入时在右侧传递的所有分支计数相加，可以同时计算小于新插入值的值数。
下面是一个Javascript代码片段来演示该方法：
function CountTree() { // tree constructor this.root = null; this.insert = function(value) { var branch = null, node = this.root, count = 0, after; while (node != null) { // traverse tree to find position branch = node; after = value > node.value; // compare to get direction if (after) { node = branch.right; // pass on the right (greater) count += branch.count;// add all nodes to the left of branch } else { node = branch.left; // pass on the left (smaller or equal) ++branch.count; // increment branch's count } } // attach new leaf if (branch == null) this.root = new Leaf(value); else if (after) branch.right = new Leaf(value); else branch.left = new Leaf(value); return count; } function Leaf(value) { // leaf constructor this.value = value; this.left = null; this.right = null; this.count = 1; }}var t = new CountTree(), v = [5, 3, 8, 2, 4, 7, 9, 1, 4, 7, 8];for (var i in v) { document.write("Inserting " + v[i] + " (found " + t.insert(v[i]) + " smaller)<BR>");}这是代码示例中的树，当插入最后一个元素（第二个值8）时。每个节点的左侧顶点（包括其自身）的节点数打印在其右侧顶点的下方。当插入第二个8时，传递值为5、8和7的节点。其中，5和7在右侧传递，它们的计数之和为6
+ 2 = 8，所以在树中有8个比8小的值：1、2、3、4、4、5、7 7.第一个值为8的节点在左侧传递，因此其计数将从3递增到4。
