中序

后序遍历
- 迭代法

src/main/java/cn/whaifree/leetCode/Tree/LeetCode145.java

@@ -0,0 +1,77 @@
+package cn.whaifree.leetCode.Tree;
+
+import cn.whaifree.leetCode.model.TreeNode;
+import org.junit.Test;
+
+import java.util.*;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/1/15 20:11
+ * @注释
+ */
+public class LeetCode145 {
+
+    @Test
+    public void test() {
+        TreeNode root = TreeNode.constructTree(new Integer[]{1, 2, 3, 4, 5});
+
+        root.printTree();
+        new Solution1().postorderTraversal(root).forEach(
+                System.out::println
+        );
+    }
+
+    class Solution {
+        List<Integer> res = new LinkedList<>();
+
+        public List<Integer> postorderTraversal(TreeNode root) {
+            if (root == null) {
+                return res;
+            }
+            postorder(root);
+            return res;
+        }
+
+        public void postorder(TreeNode root) {
+            if (root==null) return;
+
+            postorder(root.left);
+            postorder(root.right);
+            res.add(root.val);
+
+        }
+    }
+
+
+    class Solution1 {
+        public List<Integer> postorderTraversal(TreeNode root) {
+
+            List<Integer> res = new LinkedList<Integer>();
+            if (root == null) {
+                return res;
+            }
+            Deque<TreeNode> stack = new ArrayDeque<>();
+
+            stack.push(root);
+            while (!stack.isEmpty()) {
+
+                TreeNode pop = stack.pop();
+                res.add(pop.val);
+                if (pop.left != null) {
+                    stack.push(pop.left);
+                }
+                if (pop.right != null) {
+                    stack.push(pop.right);
+                }
+            }
+
+            Collections.reverse(res);
+
+            return res;
+        }
+
+    }
+
+}

src/main/java/cn/whaifree/leetCode/Tree/LeetCode94.java

@@ -0,0 +1,78 @@
+package cn.whaifree.leetCode.Tree;
+
+import cn.whaifree.leetCode.model.ListNode;
+import cn.whaifree.leetCode.model.TreeNode;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Deque;
+import java.util.LinkedList;
+import java.util.List;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/1/15 19:29
+ * @注释
+ */
+public class LeetCode94 {
+
+    @Test
+    public void test() {
+        TreeNode root = TreeNode.constructTree(new Integer[]{1, 2, 3, 4, 5});
+        TreeNode.printTree(root);
+
+        System.out.println(new Solution1().inorderTraversal(root));
+    }
+
+    class Solution {
+        List<Integer> res = new LinkedList<>();
+
+        public List<Integer> inorderTraversal(TreeNode root) {
+            if (root == null) {
+                return res;
+            }
+            inorder(root);
+            return res;
+        }
+
+        public void inorder(TreeNode root) {
+            if (root == null) {
+                return;
+            }
+            inorder(root.left);
+            res.add(root.val);
+            inorder(root.right);
+        }
+
+    }
+
+    class Solution1 {
+
+
+        public List<Integer> inorderTraversal(TreeNode root) {
+
+            List<Integer> list = new LinkedList<Integer> ();
+            if (root == null) {
+                return list;
+            }
+            Deque<TreeNode> stack = new LinkedList<>();
+
+            TreeNode index = root;
+            while (!stack.isEmpty() || index != null) {
+                // 不断左边加入，弹出获取右边的
+                // 每次循环处理一次节点，左边，右边和中间
+                if (index != null) {
+                    stack.push(index);
+                    index = index.left;
+                } else {
+                    index = stack.pop();
+                    list.add(index.val);
+                    index = index.right;
+                }
+            }
+            return list;
+        }
+
+    }
+}

src/main/java/cn/whaifree/leetCode/model/TreeNode.java

@@ -55,6 +55,10 @@ public class TreeNode {
         printNodeInternal(Collections.singletonList(root), 1, maxLevel);
     }
 
+    public void printTree() {
+        printTree(this);
+    }
+
     private static void printNodeInternal(List<TreeNode> nodes, int level, int maxLevel) {
         if (nodes == null || nodes.isEmpty() || isAllElementsNull(nodes)) {
             return;