当我为计算二叉搜索树的高度的方法运行我的代码时,它会导致堆栈溢出错误,但仅适用于具有多个节点的树(我的程序中的BSTElements)。我已经读过这是由于错误的递归调用,但无法识别我的代码中的问题。
public int getHeight() {
return getHeight(this.getRoot());
}
private int getHeight(BSTElement<String,MorseCharacter> element) {
int height=0;
if (element == null) {
return -1;
}
int leftHeight = getHeight(element.getLeft());
int rightHeight = getHeight(element.getRight());
if (leftHeight > rightHeight) {
height = leftHeight;
} else {
height = rightHeight;
}
return height +1;
}
这是完整的代码:
public class MorseCodeTree {
private static BSTElement<String, MorseCharacter> rootElement;
public BSTElement<String, MorseCharacter> getRoot() {
return rootElement;
}
public static void setRoot(BSTElement<String, MorseCharacter> newRoot) {
rootElement = newRoot;
}
public MorseCodeTree(BSTElement<String,MorseCharacter> element) {
rootElement = element;
}
public MorseCodeTree() {
rootElement = new BSTElement("Root", "", new MorseCharacter('\0', null));
}
public int getHeight() {
return getHeight(this.getRoot());
}
private int getHeight(BSTElement<String,MorseCharacter> element) {
if (element == null) {
return -1;
} else {
int leftHeight = getHeight(element.getLeft());
int rightHeight = getHeight(element.getRight());
if (leftHeight < rightHeight) {
return rightHeight + 1;
} else {
return leftHeight + 1;
}
}
}
public static boolean isEmpty() {
return (rootElement == null);
}
public void clear() {
rootElement = null;
}
public static void add(BSTElement<String,MorseCharacter> newElement) {
BSTElement<String, MorseCharacter> target = rootElement;
String path = "";
String code = newElement.getKey();
for (int i=0; i<code.length(); i++) {
if (code.charAt(i)== '.') {
if (target.getLeft()!=null) {
target=target.getLeft();
} else {
target.setLeft(newElement);
target=target.getLeft();
}
} else {
if (target.getRight()!=null) {
target=target.getRight();
} else {
target.setRight(newElement);
target=target.getRight();
}
}
}
MorseCharacter newMorseChar = newElement.getValue();
newElement.setLabel(Character.toString(newMorseChar.getLetter()));
newElement.setKey(Character.toString(newMorseChar.getLetter()));
newElement.setValue(newMorseChar);
}
public static void main(String[] args) {
MorseCodeTree tree = new MorseCodeTree();
BufferedReader reader;
try {
reader = new BufferedReader(new FileReader(file));
String line = reader.readLine();
while (line != null) {
String[] output = line.split(" ");
String letter = output[0];
MorseCharacter morseCharacter = new MorseCharacter(letter.charAt(0), output[1]);
BSTElement<String, MorseCharacter> bstElement = new BSTElement(letter, output[1], morseCharacter);
tree.add(bstElement);
line = reader.readLine();
System.out.println(tree.getHeight());
}
reader.close();
} catch (IOException e) {
System.out.println("Exception" + e);
}
您向我们展示的代码似乎没有任何明显的错误1。
如果此代码为小树提供StackOverflowException
,则很可能意味着您的树已被错误地创建并且其中有一个循环(循环)。如果递归算法遇到“树”中的循环,它将循环直到堆栈溢出2。
为了确保这种诊断,我们需要看到一个MVCE,其中包含构建展示该行为的示例树所需的所有代码。
1 - 高度计算中可能存在“off by one”错误,但这不会导致堆栈溢出。
2 - 当前的Java实现不进行尾调用优化。
请首先检查您的树是否创建错误。
否则,很可能是因为你的身高变量。当您的程序执行递归调用时,它始终启动为0,从而导致无法输出。
如果您创建了自己的节点类,就像这样:
/* Class containing left and right child of current
node and key value*/
class Node {
int element;
Node left, right;
Node(int item) {
element = item;
left = right = null;
}
Node(int item, Node left, Node right) {
element = item;
this.left = left;
this.right = right;
}
}
然后,你的getHeight类应该是这样的:
int nodesHeightFinder(Node n) {
if(n == null) return -1; /*As, if a tree has no nodes, it should not have any height.*/
else {
int heightOfLeftSubtree = nodesHeightFinder(n.left);
int heightOfRightSubtree = nodesHeightFinder(n.right);
if(heightOfLeftSubtree < heightOfRightSubtree) {
return heightOfRightSubtree + 1;
} else {
return heightOfLeftSubtree + 1;
}
}
}
希望能帮助到你!