LeetCode in Kotlin
111. Minimum Depth of Binary Tree
Easy
Given a binary tree, find its minimum depth.
The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.
Note: A leaf is a node with no children.
Example 1:
Input: root = [3,9,20,null,null,15,7]
Output: 2
Example 2:
Input: root = [2,null,3,null,4,null,5,null,6]
Output: 5
Constraints:
- The number of nodes in the tree is in the range
[0, 105]. -1000 <= Node.val <= 1000
Solution
import com_github_leetcode.TreeNode
import java.util.LinkedList
import java.util.Queue
/*
* Example:
* var ti = TreeNode(5)
* var v = ti.`val`
* Definition for a binary tree node.
* class TreeNode(var `val`: Int) {
* var left: TreeNode? = null
* var right: TreeNode? = null
* }
*/
class Solution {
fun minDepth(root: TreeNode?): Int {
if (root == null) {
return 0
}
val queue: Queue<TreeNode> = LinkedList()
queue.add(root)
var d = 0
while (queue.isNotEmpty()) {
val size: Int = queue.size
for (i in 0 until size) {
val current: TreeNode = queue.poll()
if (current.left == null && current.right == null && d > 0) {
return d + 1
}
if (current.right != null) {
queue.add(current.right)
}
if (current.left != null) {
queue.add(current.left)
}
}
d++
}
return d
}
}