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前言
这道题的难点在于要一直剪枝,直到没有值为 0 的叶子节点为止,只有从后序遍历位置自底向上处理才能获得最高的效率
一、力扣814. 二叉树剪枝
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public TreeNode pruneTree(TreeNode root) {
if(root == null){
return null;
}
root.left = pruneTree(root.left);
root.right = pruneTree(root.right);
if(root.left == null && root.right == null){
if(root.val == 0){
return null;
}
}
return root;
}
}
二、力扣1325. 删除给定值的叶子节点
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public TreeNode removeLeafNodes(TreeNode root, int target) {
if(root == null){
return null;
}
TreeNode left = removeLeafNodes(root.left,target);
TreeNode right = removeLeafNodes(root.right,target);
if(left == null && right == null){
if(root.val == target){
return null;
}
}
root.left = left;
root.right = right;
return root;
}
}