[英]Finding a node in a binary search tree in java?
I am trying to write a method that returns the depth of a target int in a binary search tree. 我正在尝试编写一种方法,该方法返回二进制搜索树中目标int的深度。 Right now it works for some smaller trees, but not always. 目前,它适用于一些较小的树木,但并非总是如此。 Does anyone see where I may be going wrong? 有人看到我可能出问题了吗?
static int count=1;
public static int findDepth(TreeNode<Integer> root, int target)
// pre: 0 or more elements in the tree, integer to search for
// post: return depth of target if found, -1 otherwise
{
count++;
if (root!=null)
{
if (root.getValue()<target)
{
if (root.getValue()==target)
{System.out.println(count);
return count;}
else
{findDepth(root.getLeft(), target);
count--;
findDepth(root.getRight(), target);
}
}
else if (root.getValue()>target)
{
if (root.getValue()==target)
{System.out.println(count);
return count;}
else
{findDepth(root.getLeft(), target);
count--;
findDepth(root.getRight(), target);
}
}
else if (root.getValue()==target)
return 1;
else
return -1;
}
return count;
}
There's a few things wrong. 有一些错误。
It will never get into this case: 它永远不会进入这种情况:
if (root.getValue()<target)
{
if (root.getValue()==target)
{System.out.println(count);
return count;}
Also it will never get into this case: 而且它永远不会进入这种情况:
else if (root.getValue()>target)
{
if (root.getValue()==target)
{System.out.println(count);
return count;}
The biggest issue is that you're keeping a global static count, and recursively going through both left and right paths. 最大的问题是您要保持全局静态计数,并递归地遍历左右路径。
First of all, for a BST, there is no need to go both left and right. 首先,对于BST,无需同时左右移动。
Second, it's better to pass the count through a parameter rather than keeping a global. 其次,最好通过参数传递计数,而不要保留全局变量。
Rather than fix your code, I'll post this working example for you to use as a reference: 我将发布此工作示例供您参考,而不是修改您的代码:
public class Main
{
public static void main(String[] args)
{
BinaryTree tree = new BinaryTree();
tree.add(20);
tree.add(10);
tree.add(30);
tree.add(15);
tree.add(25);
tree.add(5);
tree.add(35);
tree.add(1);
tree.add(6);
tree.add(14);
tree.add(16);
tree.add(24);
tree.add(26);
tree.add(34);
tree.add(36);
int level = tree.getLevel(6);
System.out.println(level);
}
}
public class TreeNode
{
int data;
TreeNode left;
TreeNode right;
public TreeNode(int d){
data = d;
left = null;
right = null;
}
}
public class BinaryTree
{
TreeNode root;
public BinaryTree(){
root = null;
}
public int getLevel(int val) {
if (root == null) return 0;
return getLevelHelper(root, val, 0);
}
public int getLevelHelper(TreeNode node, int val, int level){
int retVal = -1;
if (node.data == val){
return level;
}
if (val < node.data && node.left != null){
retVal = getLevelHelper(node.left, val, level + 1);
}
else if (val > node.data && node.right != null){
retVal = getLevelHelper(node.right, val, level + 1);
}
return retVal;
}
public boolean add(int newData){
if (root == null){
root = new TreeNode(newData);
return true;
}
else{
TreeNode curr = root;
while (true){
if (curr.data == newData){
return false;
}
else if (curr.data > newData){
if (curr.left == null){
curr.left = new TreeNode(newData);
return true;
}
else{
curr = curr.left;
}
}
else{
if (curr.right == null){
curr.right = new TreeNode(newData);
return true;
}
else{
curr = curr.right;
}
}
}
}
}
}
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