1325. Delete Leaves With a Given Value

Given a binary tree root and an integer target, delete all the leaf nodes with value target.

Note that once you delete a leaf node with value targetif it's parent node becomes a leaf node and has the value target, it should also be deleted (you need to continue doing that until you can't).

 

Example 1:

Input: root = [1,2,3,2,null,2,4], target = 2
Output: [1,null,3,null,4]
Explanation: Leaf nodes in green with value (target = 2) are removed (Picture in left). 
After removing, new nodes become leaf nodes with value (target = 2) (Picture in center).

Example 2:

Input: root = [1,3,3,3,2], target = 3
Output: [1,3,null,null,2]

Example 3:

Input: root = [1,2,null,2,null,2], target = 2
Output: [1]
Explanation: Leaf nodes in green with value (target = 2) are removed at each step.

Example 4:

Input: root = [1,1,1], target = 1
Output: []

Example 5:

Input: root = [1,2,3], target = 1
Output: [1,2,3]

 

Constraints:

  • 1 <= target <= 1000
  • The given binary tree will have between 1 and 3000 nodes.
  • Each node's value is between [1, 1000].

Rust Solution

struct Solution;
use rustgym_util::*;

trait Postorder {
    fn postorder(self, target: i32) -> Self;
}

impl Postorder for TreeLink {
    fn postorder(self, target: i32) -> Self {
        if let Some(node) = self {
            let val = node.borrow().val;
            let left = node.borrow_mut().left.take();
            let right = node.borrow_mut().right.take();
            let left = left.postorder(target);
            let right = right.postorder(target);
            if left.is_none() && right.is_none() && val == target {
                None
            } else {
                tree!(val, left, right)
            }
        } else {
            None
        }
    }
}

impl Solution {
    fn remove_leaf_nodes(root: TreeLink, target: i32) -> TreeLink {
        root.postorder(target)
    }
}

#[test]
fn test() {
    let root = tree!(1, tree!(2, tree!(2), None), tree!(3, tree!(2), tree!(4)));
    let target = 2;
    let res = tree!(1, None, tree!(3, None, tree!(4)));
    assert_eq!(Solution::remove_leaf_nodes(root, target), res);
    let root = tree!(1, tree!(3, tree!(3), tree!(2)), tree!(3));
    let target = 3;
    let res = tree!(1, tree!(3, None, tree!(2)), None);
    assert_eq!(Solution::remove_leaf_nodes(root, target), res);
    let root = tree!(1, tree!(2, tree!(2, tree!(2), None), None), None);
    let target = 2;
    let res = tree!(1);
    assert_eq!(Solution::remove_leaf_nodes(root, target), res);
}

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