662. Maximum Width of Binary Tree

Given a binary tree, write a function to get the maximum width of the given tree. The maximum width of a tree is the maximum width among all levels.

The width of one level is defined as the length between the end-nodes (the leftmost and right most non-null nodes in the level, where the `null` nodes between the end-nodes are also counted into the length calculation.

It is guaranteed that the answer will in the range of 32-bit signed integer.

Example 1:

```Input:

1
/   \
3     2
/ \     \
5   3     9

Output: 4
Explanation: The maximum width existing in the third level with the length 4 (5,3,null,9).
```

Example 2:

```Input:

1
/
3
/ \
5   3

Output: 2
Explanation: The maximum width existing in the third level with the length 2 (5,3).
```

Example 3:

```Input:

1
/ \
3   2
/
5

Output: 2
Explanation: The maximum width existing in the second level with the length 2 (3,2).
```

Example 4:

```Input:

1
/ \
3   2
/     \
5       9
/         \
6           7
Output: 8
Explanation:The maximum width existing in the fourth level with the length 8 (6,null,null,null,null,null,null,7).
```

Constraints:

• The given binary tree will have between `1` and `3000` nodes.

662. Maximum Width of Binary Tree
``````struct Solution;
use rustgym_util::*;
use std::collections::HashMap;

trait Preorder {
fn preorder(
&self,
row: usize,
pos: u32,
min: &mut HashMap<usize, u32>,
max: &mut HashMap<usize, u32>,
diff: &mut u32,
);
}

fn preorder(
&self,
row: usize,
pos: u32,
min: &mut HashMap<usize, u32>,
max: &mut HashMap<usize, u32>,
diff: &mut u32,
) {
if let Some(node) = self {
min.entry(row).or_insert(pos);
max.entry(row).or_insert(pos);
*min.get_mut(&row).unwrap() = min[&row].min(pos);
*max.get_mut(&row).unwrap() = max[&row].max(pos);
*diff = (*diff).max(max[&row] - min[&row] + 1);
let node = node.borrow();
node.left.preorder(row + 1, pos << 1, min, max, diff);
node.right.preorder(row + 1, (pos << 1) + 1, min, max, diff);
}
}
}

impl Solution {
fn width_of_binary_tree(root: TreeLink) -> i32 {
let mut min: HashMap<usize, u32> = HashMap::new();
let mut max: HashMap<usize, u32> = HashMap::new();
let mut res = 0;
root.preorder(0, 0, &mut min, &mut max, &mut res);
res as i32
}
}

#[test]
fn test() {
let root = tree!(1, tree!(3, tree!(5), tree!(3)), tree!(2, None, tree!(9)));
let res = 4;
assert_eq!(Solution::width_of_binary_tree(root), res);
let root = tree!(1, tree!(3, tree!(5), tree!(3)), None);
let res = 2;
assert_eq!(Solution::width_of_binary_tree(root), res);
let root = tree!(1, tree!(3, tree!(5), None), tree!(2));
let res = 2;
assert_eq!(Solution::width_of_binary_tree(root), res);
let root = tree!(
1,
tree!(3, tree!(5, tree!(6), None), None),
tree!(2, None, tree!(9, None, tree!(7)))
);
let res = 8;
assert_eq!(Solution::width_of_binary_tree(root), res);
}
``````