Given the root of a Binary Search Tree and a target number k, return true if there exist two elements in the BST such that their sum is equal to the given target.
Example 1:
Input: root = [5,3,6,2,4,null,7], k = 9 Output: true
Example 2:
Input: root = [5,3,6,2,4,null,7], k = 28 Output: false
Example 3:
Input: root = [2,1,3], k = 4 Output: true
Example 4:
Input: root = [2,1,3], k = 1 Output: false
Example 5:
Input: root = [2,1,3], k = 3 Output: true
Constraints:
- The number of nodes in the tree is in the range
[1, 104]. -104 <= Node.val <= 104rootis guaranteed to be a valid binary search tree.-105 <= k <= 105
struct Solution;
use rustgym_util::*;
use std::cmp::Ordering::*;
trait Inorder {
fn inorder(&self, v: &mut Vec<i32>, target: i32);
}
impl Inorder for TreeLink {
fn inorder(&self, v: &mut Vec<i32>, target: i32) {
if let Some(node) = self {
let node = node.borrow();
let left = &node.left;
let right = &node.right;
Self::inorder(left, v, target);
v.push(node.val);
Self::inorder(right, v, target);
}
}
}
impl Solution {
fn find_target(root: TreeLink, k: i32) -> bool {
let mut v = vec![];
root.inorder(&mut v, k);
let n = v.len();
let mut l = 0;
let mut r = n - 1;
while l < r {
let sum = v[l] + v[r];
match sum.cmp(&k) {
Greater => {
r -= 1;
}
Less => {
l += 1;
}
Equal => {
return true;
}
}
}
false
}
}
#[test]
fn test() {
let root = tree!(5, tree!(3, tree!(2), tree!(4)), tree!(6, None, tree!(7)));
assert_eq!(Solution::find_target(root, 9), true);
}