2018-10-10 22:03:03 +00:00
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---
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id: 587d8258367417b2b2512c82
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2020-12-16 07:37:30 +00:00
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title: 在二叉搜索树中删除具有两个子节点的节点
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2018-10-10 22:03:03 +00:00
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challengeType: 1
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videoUrl: ''
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---
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2020-12-16 07:37:30 +00:00
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# --description--
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删除具有两个子节点的节点是最难实现的。删除这样的节点会生成两个不再连接到原始树结构的子树。我们如何重新连接它们?一种方法是在目标节点的右子树中找到最小值,并用该值替换目标节点。以这种方式选择替换确保它大于左子树中的每个节点,它成为新的父节点,但也小于右子树中的每个节点,它成为新的父节点。完成此替换后,必须从右子树中删除替换节点。即使这个操作也很棘手,因为替换可能是一个叶子,或者它本身可能是一个右子树的父亲。如果是叶子,我们必须删除其父对它的引用。否则,它必须是目标的正确子项。在这种情况下,我们必须用替换值替换目标值,并使目标引用替换的右子。说明:让我们通过处理第三种情况来完成我们的`remove`方法。我们为前两种情况再次提供了一些代码。现在添加一些代码来处理具有两个子节点的目标节点。任何边缘情况要注意?如果树只有三个节点怎么办?完成后,这将完成二进制搜索树的删除操作。干得好,这是一个非常难的问题!
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# --hints--
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存在`BinarySearchTree`数据结构。
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```js
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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}
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return typeof test == 'object';
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})()
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);
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```
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二叉搜索树有一个名为`remove`的方法。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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} else {
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return false;
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}
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return typeof test.remove == 'function';
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})()
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);
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2018-10-10 22:03:03 +00:00
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```
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2020-12-16 07:37:30 +00:00
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尝试删除不存在的元素将返回`null` 。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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} else {
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return false;
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}
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return typeof test.remove == 'function' ? test.remove(100) == null : false;
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})()
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);
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```
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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如果根节点没有子节点,则删除它会将根节点设置为`null` 。
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2018-10-10 22:03:03 +00:00
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```js
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2020-12-16 07:37:30 +00:00
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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} else {
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return false;
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}
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test.add(500);
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test.remove(500);
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return typeof test.remove == 'function' ? test.inorder() == null : false;
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})()
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);
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```
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`remove`方法从树中删除叶节点
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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} else {
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return false;
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}
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test.add(5);
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test.add(3);
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test.add(7);
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test.add(6);
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test.add(10);
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test.add(12);
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test.remove(3);
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test.remove(12);
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test.remove(10);
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return typeof test.remove == 'function'
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? test.inorder().join('') == '567'
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: false;
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})()
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);
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2018-10-10 22:03:03 +00:00
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```
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2020-12-16 07:37:30 +00:00
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`remove`方法删除具有一个子节点的节点。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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} else {
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return false;
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}
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if (typeof test.remove !== 'function') {
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return false;
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}
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test.add(-1);
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test.add(3);
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test.add(7);
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test.add(16);
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test.remove(16);
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test.remove(7);
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test.remove(3);
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return test.inorder().join('') == '-1';
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})()
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);
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```
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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删除具有两个节点的树中的根将第二个节点设置为根。
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2018-10-10 22:03:03 +00:00
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```js
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2020-12-16 07:37:30 +00:00
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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} else {
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return false;
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}
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if (typeof test.remove !== 'function') {
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return false;
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}
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test.add(15);
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test.add(27);
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test.remove(15);
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return test.inorder().join('') == '27';
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})()
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);
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2018-10-10 22:03:03 +00:00
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```
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2020-12-16 07:37:30 +00:00
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`remove`方法在保留二叉搜索树结构的同时删除具有两个子节点的节点。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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} else {
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return false;
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}
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if (typeof test.remove !== 'function') {
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return false;
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}
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test.add(1);
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test.add(4);
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test.add(3);
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test.add(7);
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test.add(9);
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test.add(11);
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test.add(14);
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test.add(15);
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test.add(19);
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test.add(50);
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test.remove(9);
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if (!test.isBinarySearchTree()) {
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return false;
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}
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test.remove(11);
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if (!test.isBinarySearchTree()) {
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return false;
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}
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test.remove(14);
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if (!test.isBinarySearchTree()) {
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return false;
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}
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test.remove(19);
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if (!test.isBinarySearchTree()) {
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return false;
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}
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test.remove(3);
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if (!test.isBinarySearchTree()) {
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return false;
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}
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test.remove(50);
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if (!test.isBinarySearchTree()) {
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return false;
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}
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test.remove(15);
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if (!test.isBinarySearchTree()) {
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return false;
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}
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return test.inorder().join('') == '147';
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})()
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);
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```
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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可以在三个节点的树上删除根。
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2018-10-10 22:03:03 +00:00
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```js
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2020-12-16 07:37:30 +00:00
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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} else {
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return false;
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}
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if (typeof test.remove !== 'function') {
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return false;
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}
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test.add(100);
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test.add(50);
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test.add(300);
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test.remove(100);
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return test.inorder().join('') == 50300;
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})()
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);
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2018-10-10 22:03:03 +00:00
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```
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2020-08-13 15:24:35 +00:00
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2020-12-16 07:37:30 +00:00
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# --solutions--
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