[英]Store a counter in a binary tree recursive function in java
我在学校做一个练习,我必须在java中创建一个方法(最多O(n)时间),该方法存储给定值在二叉树中出现的顺序,无论是后顺序,按顺序还是按顺序预遍历。 到目前为止,我有有效的代码,但是计数器不能正确递增。 有人可以让我知道我在做什么错吗? 我的代码如下:
public class Node {
int value; // data used as key value
Node left; // this node's left child
Node right; // this node's right child
int preorderNumber; // node number in preorder
int inorderNumber; // node number in inorder
int postorderNumber; // node number in postorder
public Node(int item) { //instantiates node.
value = item;
left = right = null;
preorderNumber = inorderNumber = postorderNumber = 0;
}
}
/* Given a binary tree, print its nodes according to the postorder traversal. */
private void printPostorder(Node node) {
int counter = 0;
if (node == null) { //the tree is empty.
return;
}
printPostorder(node.left); // first recur on left subtree
printPostorder(node.right); // then recur on right subtree
System.out.print(node.value + " "); // now deal with the node
counter++;
node.postorderNumber = counter;
}
/* Given a binary tree, print its nodes in inorder*/
private void printInorder(Node node) {
int counter = 0;
if (node == null) {
return;
}
printInorder(node.left); // first recur on left child
System.out.print(node.value + " "); // then print the data of node
counter++;
node.inorderNumber = counter;
printInorder(node.right); // now recur on right child
}
/* Given a binary tree, print its nodes in preorder*/
private void printPreorder(Node node) {
int counter = 0;
if (node == null) { //binary tree is empty.
return;
}
System.out.print(node.value + " "); // first print data of node.
counter++;
node.preorderNumber = counter;
printPreorder(node.left); // recur on left subtree
printPreorder(node.right); // now recur on right subtree
}
public int find(int valueToFind) {
Node current = root, prior = null;
while (current != null) {
int compare;
compare = (valueToFind - current.value);
if (compare < 0) {
prior = current;
current = current.left;
} else if (compare > 0) {
current = current.right;
} else {
System.out.println("The node value searched for is : " + valueToFind);
System.out.println("The in order value is: " + current.inorderNumber);
System.out.println("The post order value is: " + current.postorderNumber);
System.out.println("The pre order value is: " + current.preorderNumber);
return current.value;
}
}
return prior == null ? null : prior.value;
}
}
每当我尝试运行此命令时,都会得到类似以下输出的信息:
节点数为:2二叉树的顺序遍历为3 4二叉树的顺序遍历为3 4二叉树的后顺序遍历为4 3搜索的节点值为:4顺序值是:1后顺序值是:1预定值是:1
我不确定如何将计数器的值传递给节点,以便它保留正确的值(在这种情况下,为2、2和1)。 谢谢!
您需要从prv值获取计数器。 否则,它将一直被重置。 像下面那样做
private void printPostorder(Node node) {
if (node == null) { //the tree is empty.
return;
}
int counter = node.postorderNumber;
printPostorder(node.left); // first recur on left subtree
printPostorder(node.right); // then recur on right subtree
System.out.print(node.value + " "); // now deal with the node
counter++;
node.postorderNumber = counter;
}
预购方法也应该像这样改变,否则计数器不会增加
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