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Binary Tree Pruning.java
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37 lines (36 loc) · 914 Bytes
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/**
* 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) {
boolean isRootOne = helper(root);
return isRootOne ? root : null;
}
private boolean helper(TreeNode root) {
if (root == null) {
return false;
}
boolean selfOne = root.val == 1;
boolean leftContainsOne = helper(root.left);
boolean rightContainsOne = helper(root.right);
if (!leftContainsOne) {
root.left = null;
}
if (!rightContainsOne) {
root.right = null;
}
return selfOne || leftContainsOne || rightContainsOne;
}
}