Merge pull request #108 from Joshua-Lu/patch-25

更新 0700.二叉搜索树中的搜索 Java版本

problems/0700.二叉搜索树中的搜索.md

@@ -141,24 +141,62 @@ public:
 ## 其他语言版本
 
 Java：
-递归法：
 
-
-```java
+```Java
 class Solution {
+    // 递归，普通二叉树
     public TreeNode searchBST(TreeNode root, int val) {
-        if (root == null) return null;
-        if (root.val == val) return root;
-        else if (root.val > val) return searchBST(root.left, val);
-        else return searchBST(root.right, val);
+        if (root == null || root.val == val) {
+            return root;
+        }
+        TreeNode left = searchBST(root.left, val);
+        if (left != null) {
+            return left;
+        }
+        return searchBST(root.right, val);
     }
 }
-```
 
-迭代法：
-
-```java
 class Solution {
+    // 递归，利用二叉搜索树特点，优化
+    public TreeNode searchBST(TreeNode root, int val) {
+        if (root == null || root.val == val) {
+            return root;
+        }
+        if (val < root.val) {
+            return searchBST(root.left, val);
+        } else {
+            return searchBST(root.right, val);
+        }
+    }
+}
+
+class Solution {
+    // 迭代，普通二叉树
+    public TreeNode searchBST(TreeNode root, int val) {
+        if (root == null || root.val == val) {
+            return root;
+        }
+        Stack<TreeNode> stack = new Stack<>();
+        stack.push(root);
+        while (!stack.isEmpty()) {
+            TreeNode pop = stack.pop();
+            if (pop.val == val) {
+                return pop;
+            }
+            if (pop.right != null) {
+                stack.push(pop.right);
+            }
+            if (pop.left != null) {
+                stack.push(pop.left);
+            }
+        }
+        return null;
+    }
+}
+
+class Solution {
+    // 迭代，利用二叉搜索树特点，优化，可以不需要栈
     public TreeNode searchBST(TreeNode root, int val) {
         while (root != null)
             if (val < root.val) root = root.left;