Delete the subtree of the node whose value is x
topic
It is known that the binary tree is stored in a binary linked list, and the algorithm is completed: for each node whose element value is x in the tree, delete the subtree rooted at it, and release the corresponding space.
idea
- To delete the subtree rooted at element value x, as long as its left and right subtrees can be deleted, the root node with value x can be released, so it is advisable to use post-order traversal. [Pre/Middle/Sequential]
- **Algorithm idea: **Deleting a node with a value of x means that the left (right) child pointer of its parent node should be empty, and it is easy to find the parent node of a node with hierarchical traversal. This question requires to delete the subtree of the node whose element value is × in the tree, so it is necessary to traverse the complete binary tree. 【BFS】
coding
/**
* 删除当前结点
*
* @param root 根节点
*/
public void removeChildNodes(TreeNode root) {
if (root != null) {
removeChildNodes(root.left);
removeChildNodes(root.right);
//这里我假设val=-1就是无效结点，也就是被删除了
root.val = -1;
}
}
/**
* 搜索结点值为x的元素
*
* @param root 根元素
* @param x 要比对的值
*/
public void searchNodesAndDel(TreeNode root, int x) {
if (root != null) {
if (root.val == x) {
removeChildNodes(root.left);
//root.left = null;
removeChildNodes(root.right);
//root.right = null;
}
searchNodesAndDel(root.left, x);
searchNodesAndDel(root.right, x);
}
}