package com.github.masx200.leetcode_test.binary_search_tree_iterator

Author: masx200

binary-search-tree-iterator/index.kt

@@ -0,0 +1,27 @@
+package com.github.masx200.leetcode_test.binary_search_tree_iterator
+
+import com.github.masx200.leetcode_test.insert_into_a_binary_search_tree.TreeNode
+
+class BSTIterator(root: TreeNode?) {
+    private val generator = InOrderIterator(root).iterator()
+    fun next(): Int {
+        return this.generator.next()
+    }
+
+    fun hasNext(): Boolean {
+        return this.generator.hasNext()
+    }
+
+}
+
+fun InOrderIterator(root: TreeNode?): Sequence<Int> {
+    return sequence {
+
+        if (root == null) return@sequence
+
+        yieldAll(InOrderIterator(root.left))
+        yield(root.`val`)
+        yieldAll(InOrderIterator(root.right))
+    }
+}
+

pom.xml

@@ -86,6 +86,7 @@
                         </goals>
                         <configuration>
                             <sourceDirs>
+                                <sourceDir>binary-search-tree-iterator</sourceDir>
                                 <sourceDir>construct-binary-search-tree-from-preorder-traversal</sourceDir>
                                 <source>er-cha-shu-ran-se-UGC</source>
                                 <source>er-cha-sou-suo-shu-de-di-kda-jie-dian-lcof</source>

test/com/github/masx200/leetcode_test/binary_search_tree_iterator/BSTIteratorTest.kt

@@ -0,0 +1,20 @@
+package com.github.masx200.leetcode_test.binary_search_tree_iterator
+
+import com.github.masx200.leetcode_test.utils.TreeNodeLeetCodeParse
+import org.junit.jupiter.api.Test
+import kotlin.test.assertContentEquals
+
+internal class BSTIteratorTest {
+
+    @Test
+    fun testnext() {
+        val iterator = BSTIterator(TreeNodeLeetCodeParse("[7, 3, 15, null, null, 9, 20]"))
+
+        val res = mutableListOf<Int>()
+        while (iterator.hasNext()) {
+            res.add(iterator.next())
+        }
+        assertContentEquals(res, listOf(3, 7, 9, 15, 20))
+
+    }
+}