Given a binary tree, find the leftmost value in the last row of the tree.
Example 1:
Input:
2
/ \
1 3
Output:
1
**Example 2: **
Input:
1
/ \
2 3
/ / \
4 5 6
/
7
Output:
7
Note: You may assume the tree (i.e., the given root node) is not NULL.
/**
* Definition for a binary tree node.
* public class TreeNode {
* public var val: Int
* public var left: TreeNode?
* public var right: TreeNode?
* public init(_ val: Int) {
* self.val = val
* self.left = nil
* self.right = nil
* }
* }
*/
class Solution {
func findBottomLeftValue(_ root: TreeNode?) -> Int {
guard let r = root else { return 0 }
var layer = [r]
var lastLeft = r
while layer.count > 0 {
for i in 0..<layer.count {
let n = layer.removeFirst()
if let l = n.left { layer.append(l) }
if let r = n.right { layer.append(r) }
}
lastLeft = layer.first ?? lastLeft
}
return lastLeft.val
}
}