添加 0530.二叉搜索树的最小绝对差.md Scala版本

problems/0530.二叉搜索树的最小绝对差.md

@@ -431,7 +431,84 @@ function getMinimumDifference(root: TreeNode | null): number {
 };
 ```
 
+## Scala
 
+构建二叉树的有序数组:
+
+```scala
+object Solution {
+  import scala.collection.mutable
+  def getMinimumDifference(root: TreeNode): Int = {
+    val arr = mutable.ArrayBuffer[Int]()
+    def traversal(node: TreeNode): Unit = {
+      if (node == null) return
+      traversal(node.left)
+      arr.append(node.value)
+      traversal(node.right)
+    }
+    traversal(root)
+    // 在有序数组上求最小差值
+    var result = Int.MaxValue
+    for (i <- 1 until arr.size) {
+      result = math.min(result, arr(i) - arr(i - 1))
+    }
+    result // 返回最小差值
+  }
+}
+```
+
+递归记录前一个节点:
+
+```scala
+object Solution {
+  def getMinimumDifference(root: TreeNode): Int = {
+    var result = Int.MaxValue // 初始化为最大值
+    var pre: TreeNode = null // 记录前一个节点
+
+    def traversal(cur: TreeNode): Unit = {
+      if (cur == null) return
+      traversal(cur.left)
+      if (pre != null) {
+        // 对比result与节点之间的差值
+        result = math.min(result, cur.value - pre.value)
+      }
+      pre = cur
+      traversal(cur.right)
+    }
+
+    traversal(root)
+    result // return关键字可以省略
+  }
+}
+```
+
+迭代解决:
+
+```scala
+object Solution {
+  import scala.collection.mutable
+  def getMinimumDifference(root: TreeNode): Int = {
+    var result = Int.MaxValue // 初始化为最大值
+    var pre: TreeNode = null // 记录前一个节点
+    var cur = root
+    var stack = mutable.Stack[TreeNode]()
+    while (cur != null || !stack.isEmpty) {
+      if (cur != null) {
+        stack.push(cur)
+        cur = cur.left
+      } else {
+        cur = stack.pop()
+        if (pre != null) {
+          result = math.min(result, cur.value - pre.value)
+        }
+        pre = cur
+        cur = cur.right
+      }
+    }
+    result // return关键字可以省略
+  }
+}
+```
 
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>