fd

Author: dingjikerbo

leetcode/solution/src/KthSmallestElementInBST.java

@@ -14,30 +14,6 @@
 public class KthSmallestElementInBST {
 
     public int kthSmallest(TreeNode root, int k) {
-        int[] kth = new int[1];
-        inorderTraversal(root, k, kth);
-        return kth[0];
-    }
-
-    private int inorderTraversal(TreeNode root, int k, int[] kth) {
-        if (root == null) {
-            return k;
-        }
-
-        k = inorderTraversal(root.left, k, kth);
-
-        if (--k == 0) {
-            kth[0] = root.val;
-            return 0;
-        }
-
-        return inorderTraversal(root.right, k, kth);
-    }
-
-    /**
-     * 非递归法
-     */
-    public int kthSmallest2(TreeNode root, int k) {
         Stack<TreeNode> stack = new Stack<>();
         while (root != null || !stack.isEmpty()) {
             if (root != null) {
@@ -59,7 +35,7 @@ public int kthSmallest2(TreeNode root, int k) {
     /**
      * Morris
      */
-    private int kthSmallest3(TreeNode root, int k) {
+    private int kthSmallest2(TreeNode root, int k) {
         TreeNode temp;
 
         while (root != null) {

leetcode/src/Main.java

@@ -4,29 +4,23 @@
 
 public class Main {
 
-    public static int diameterOfBinaryTree(TreeNode root) {
-        if (root == null) {
-            return 0;
+    public int kthSmallest(TreeNode root, int k) {
+        Stack<TreeNode> stack = new Stack<>();
+        while (!stack.isEmpty() || root != null) {
+            if (root != null) {
+                stack.push(root);
+                root = root.left;
+            } else {
+                root = stack.pop();
+                if (--k == 0) {
+                    return root.val;
+                }
+                root = root.right;
+            }
         }
-        return dfs(root, false);
-    }
-
-    public static int dfs(TreeNode root, boolean flag) {
-        if (root == null) {
-            return -1;
-        }
-        return flag ? Math.max(dfs(root.left, true) + 1, dfs(root.right, true) + 1) :
-                Math.max(Math.max(dfs(root.left, false), dfs(root.right, false)),
-                        dfs(root.left, true) + 2 + dfs(root.right, true));
+        return 0;
     }
 
     public static void main(String[] args) {
-        TreeNode node4 = new TreeNode(4);
-        TreeNode node5 = new TreeNode(5);
-        TreeNode node2 = new TreeNode(2, node4, node5);
-        TreeNode node3 = new TreeNode(3);
-        TreeNode node1 = new TreeNode(1, node2, node3);
-        int len = diameterOfBinaryTree(node1);
-        System.out.println(String.format("len = %d", len));
     }
 }