LeetCode in Kotlin
404. Sum of Left Leaves
Easy
Given the root of a binary tree, return the sum of all left leaves.
A leaf is a node with no children. A left leaf is a leaf that is the left child of another node.
Example 1:
Input: root = [3,9,20,null,null,15,7]
Output: 24
Explanation: There are two left leaves in the binary tree, with values 9 and 15 respectively.
Example 2:
Input: root = [1]
Output: 0
Constraints:
- The number of nodes in the tree is in the range
[1, 1000]. -1000 <= Node.val <= 1000
Solution
import com_github_leetcode.TreeNode
/*
* 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 sumOfLeftLeaves(root: TreeNode): Int {
fun dfs(root: TreeNode?, left: Boolean): Int {
root ?: return 0
if (root.left == null && root.right == null) {
return if (left) {
root.`val`
} else {
0
}
}
return dfs(root.left, true) + dfs(root.right, false)
}
return dfs(root, false)
}
}