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187 lines (168 loc) · 5.56 KB
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public class BinarySearchTree extends BinaryTree {
public BinarySearchTree(int[] nums) {
super();
this.batchInsert(nums);
}
public static TreeNode findLeftSuccessor(TreeNode node) {// 找临近值
if (node.left != null) {
TreeNode curr = node.left;
while (curr.right != null) {
curr = curr.right;
}
return curr;
}
return null;
}
public static TreeNode findRightSuccessor(TreeNode node) {
if (node.right != null) {
TreeNode curr = node.right;
while (curr.left != null) {
curr = curr.left;
}
return curr;
}
return null;
}
public void insert(int value) {
if (root == null) {
root = new TreeNode(value);
return;// 默认返回什么也不做
}
TreeNode current = root;// 不断改变的当前指针，要插入的位置
TreeNode parent;// 当前指针的父节点
while (true) {
parent = current;
if (parent.val > value) {
current = parent.left;
if (current == null) {
parent.left = new TreeNode(value);
return;
}
} else if (parent.val < value) {
current = parent.right;
if (current == null) {
parent.right = new TreeNode(value);
return;
}
} else {
return;// BST does't allow nodes with the same value;//如果相等什么都不用做直接退出
}
}
}// 因为当前指针为null的时候是没有意义的默认节点，就如所有的Leaf节点都会指向null，
// 既然是空的没意义的节点，就不能直接的赋值；
// 需借助父节点的帮助来决定需要添加left child还是right child
public void batchInsert(int[] vals) { // 批量插入
for (int v : vals) {
insert(v);// 每个元素都要调用一次插入函数
}
}
public boolean get(int value) {
if (root == null) {
return false;
}
TreeNode current = root;// current指针从root开始寻找
while (current != null && current.val != value) {// 循环跳出条件：current指针还没有迭代完且current值不等于目标值
if (current.val > value) {
current = current.left;
} else if (current.val < value) {
current = current.right;
} else {
return true;
}
}
return false;// 若迭代结束还没找到
}
public boolean delete(int key) {
TreeNode parent = root;
TreeNode current = root;
boolean isLeftChild = false;
while (current != null && current.val != key) {
parent = current;
if (current.val > key) {
isLeftChild = true;
current = current.left;
} else {
isLeftChild = false;
current = current.right;
}
}
if (current == null) {
return false;
}
// case1:if node to be deleted has no children
if (current.left == null && current.right == null) {
if (current == root) {
root = null;
} else if (isLeftChild) {
parent.left = null;
} else {
parent.right = null;
}
} else {
current.val = getSuccessor(current);
}
return true;
}
public int getSuccessor(TreeNode node) {
if (node.left != null) {
// find most right of left
TreeNode current = node.left;
TreeNode parent = node;
while (current.right != null) {
parent = current;
current = current.right;
}
int res = current.val;
if (parent == node) {
if (current.left != null) {
node.left = current.left;
} else {
node.left = null;
}
} else {
if (current.left != null) {
parent.right = current.left;
} else {
parent.right = null;
}
}
return res;
}
// find most left node of right
TreeNode current = node.right;
TreeNode parent = node;
while (current.left != null) {
parent = current;
current = current.left;
}
int res = current.val;
if (parent == node) {
if (current.right != null) {
node.right = current.right;
} else {
node.right = null;
}
} else {
if (current.right != null) {
parent.left = current.right;
} else {
parent.left = null;
}
}
return res;
}
}
/*
* BinarySearchTree bst = new BinarySearchTree(); bst.insert(10);
* bst.batchInsert(new int[] { 2, 5, 8, 12, 16, 20 }); bst.print();
*
* for (int v = 0; v <= 20; v++) { System.out.println("Delete " + v + ": " +
* bst.delete(v)); bst.print(); }
*
* bst.batchInsert(new int[] { 2, 5, 8, 12, 16, 20 }); bst.print();
*
* for (int v = 20; v >= 0; v--) { System.out.println("Delete " + v + ": " +
* bst.delete(v)); bst.print(); }
*
* bst.printPre(); //BinarySearchTree.PreOrder(bst.root);
*/