31 lines
811 B
Kotlin
31 lines
811 B
Kotlin
/**
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* Example:
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* var ti = TreeNode(5)
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* var v = ti.`val`
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* Definition for a binary tree node.
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* class TreeNode(var `val`: Int) {
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* var left: TreeNode? = null
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* var right: TreeNode? = null
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* }
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*/
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class Solution {
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private fun levelOrder(
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root: TreeNode?,
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levels: MutableList<MutableList<Int>>,
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level: Int,
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): MutableList<MutableList<Int>> {
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if (root == null) {
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return levels
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}
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if (level + 1 > levels.size) {
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levels.add(mutableListOf<Int>())
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}
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levels[level].add(root.`val`)
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levelOrder(root.left, levels, level + 1)
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return levelOrder(root.right, levels, level + 1)
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}
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fun levelOrder(root: TreeNode?): List<List<Int>> = levelOrder(root, mutableListOf<MutableList<Int>>(), 0)
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}
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