894. All Possible Full Binary Trees
A full binary tree is a binary tree where each node has exactly 0 or 2 children.
Return a list of all possible full binary trees with N nodes. Each element of the answer is the root node of one possible tree.
Each node of each tree in the answer must have node.val = 0.
You may return the final list of trees in any order.
Example 1:
Input: 7 Output: [[0,0,0,null,null,0,0,null,null,0,0],[0,0,0,null,null,0,0,0,0],[0,0,0,0,0,0,0],[0,0,0,0,0,null,null,null,null,0,0],[0,0,0,0,0,null,null,0,0]] Explanation:
Note:
1 <= N <= 20
Rust Solution
struct Solution;
use rustgym_util::*;
impl Solution {
fn all_possible_fbt(n: i32) -> Vec<TreeLink> {
if n % 2 == 0 {
return vec![];
}
if n == 1 {
vec![tree!(0)]
} else {
let mut res = vec![];
let mut l = 1;
let mut r = n - 1 - l;
while r > 0 {
let left_trees = Self::all_possible_fbt(l);
let right_trees = Self::all_possible_fbt(r);
for left in &left_trees {
for right in &right_trees {
res.push(tree!(0, left.clone(), right.clone()));
}
}
r -= 2;
l += 2;
}
res
}
}
}
#[test]
fn test() {
let n = 7;
let res = [
tree!(
0,
tree!(0),
tree!(0, tree!(0), tree!(0, tree!(0), tree!(0)))
),
tree!(
0,
tree!(0),
tree!(0, tree!(0, tree!(0), tree!(0)), tree!(0))
),
tree!(
0,
tree!(0, tree!(0), tree!(0)),
tree!(0, tree!(0), tree!(0))
),
tree!(
0,
tree!(0, tree!(0), tree!(0, tree!(0), tree!(0))),
tree!(0)
),
tree!(
0,
tree!(0, tree!(0, tree!(0), tree!(0)), tree!(0)),
tree!(0)
),
];
assert_eq!(Solution::all_possible_fbt(n), res);
}
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