diff --git a/src/main/java/cn/whaifree/leetCode/model/TreeNode.java b/src/main/java/cn/whaifree/leetCode/model/TreeNode.java
index 10e79c1..06347bd 100644
--- a/src/main/java/cn/whaifree/leetCode/model/TreeNode.java
+++ b/src/main/java/cn/whaifree/leetCode/model/TreeNode.java
@@ -1,7 +1,6 @@
 package cn.whaifree.leetCode.model;
 
 import java.util.*;
-import java.util.function.Consumer;
 
 /**
  * @version 1.0
@@ -43,6 +42,13 @@ public class TreeNode {
 //        }
 //    }
 
+
+    @Override
+    public String toString() {
+        printTree(this);
+        return null;
+    }
+
     public static List<Integer> treeToArray(TreeNode root) {
         List<Integer> result = new ArrayList<>();
         if (root == null)
diff --git a/src/main/java/cn/whaifree/redo/redoAll/2024_3_30.md b/src/main/java/cn/whaifree/redo/redoAll/2024_3_30.md
index 4b8930e..5dcb1ad 100644
--- a/src/main/java/cn/whaifree/redo/redoAll/2024_3_30.md
+++ b/src/main/java/cn/whaifree/redo/redoAll/2024_3_30.md
@@ -5,5 +5,12 @@
 [LeetCode15.java](LeetCode15.java)
 水平遍历 [LeetCode94_145_144_102.java](LeetCode94_145_144_102.java)
 
+[LeetCode199.java](LeetCode199.java)
+
+[LeetCode105.java](LeetCode105.java) 构造二叉树
+
+
+
+
 
 
diff --git a/src/main/java/cn/whaifree/redo/redoAll/LeetCode101.java b/src/main/java/cn/whaifree/redo/redoAll/LeetCode101.java
new file mode 100644
index 0000000..51180cf
--- /dev/null
+++ b/src/main/java/cn/whaifree/redo/redoAll/LeetCode101.java
@@ -0,0 +1,78 @@
+package cn.whaifree.redo.redoAll;
+
+import cn.whaifree.leetCode.model.TreeNode;
+import org.junit.Test;
+
+import java.util.Deque;
+import java.util.LinkedList;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/3/31 11:53
+ * @注释
+ */
+public class LeetCode101 {
+    @Test
+    public void test()
+    {
+        System.out.println(new Solution1().isSymmetric(TreeNode.constructTreeByArray(1,2,3)));
+    }
+
+    class Solution {
+        public boolean isSymmetric(TreeNode root) {
+            return isSyn(root.left, root.right);
+        }
+
+        public boolean isSyn(TreeNode one, TreeNode two) {
+            if (one == null && two == null) {
+                return true;
+            } else if (one == null || two == null) {
+                return false;
+            } else if (one.val != two.val) {
+                return false;
+            }
+
+            boolean a = isSyn(one.left, two.right);
+            boolean b = isSyn(one.right, two.left);
+
+            return a && b;
+        }
+    }
+
+    class Solution1 {
+        public boolean isSymmetric(TreeNode root) {
+            if (root.left == null && root.right == null) {
+                return true;
+            }else if (root.left == null || root.right == null) {
+                return false;
+            }
+
+            Deque<TreeNode> deque = new LinkedList<>();
+            deque.add(root.left);
+            deque.add(root.right);
+            while (!deque.isEmpty()) {
+                TreeNode one = deque.pop();
+                TreeNode two = deque.pop();
+                if (one != null && two == null) {
+                    return false;
+                } else if (one == null && two != null) {
+                    return false;
+                } else if (one == null && two == null) {
+                    continue;
+                }
+                if (one.val != two.val) {
+                    return false;
+                }
+                deque.add(one.left);
+                deque.add(two.right);
+                deque.add(one.right);
+                deque.add(two.left);
+            }
+
+            return true;
+        }
+
+    }
+
+}
diff --git a/src/main/java/cn/whaifree/redo/redoAll/LeetCode105.java b/src/main/java/cn/whaifree/redo/redoAll/LeetCode105.java
new file mode 100644
index 0000000..d3960d5
--- /dev/null
+++ b/src/main/java/cn/whaifree/redo/redoAll/LeetCode105.java
@@ -0,0 +1,55 @@
+package cn.whaifree.redo.redoAll;
+
+import cn.whaifree.leetCode.model.TreeNode;
+import org.junit.Test;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/3/31 13:32
+ * @注释
+ */
+public class LeetCode105 {
+    @Test
+    public void test() {
+        Solution solution = new Solution();
+        int[] preorder = {3, 9, 20, 15, 7};
+        int[] inorder = {9, 3, 15, 20, 7};
+        TreeNode treeNode = solution.buildTree(preorder, inorder);
+        treeNode.printTree();
+    }
+
+    class Solution {
+        public TreeNode buildTree(int[] preorder, int[] inorder) {
+            return build(preorder, inorder, 0, preorder.length - 1, 0, inorder.length - 1);
+        }
+
+        /**
+         * preorder = [3,9,20,15,7], inorder = [9,3,15,20,7]
+         */
+        public TreeNode build(
+                int[] preorder,
+                int[] inorder,
+                int preStart,
+                int preEnd,
+                int inStart,
+                int inEnd
+        ) {
+            if (preStart > preEnd || inStart > inEnd) {
+                return null;
+            }
+            int head = preorder[preStart];
+            TreeNode h = new TreeNode(head);
+
+            int inS = 0; // 标记中序中在哪
+            while (inorder[inS] != head) {
+                inS++;
+            }
+            int l = inS - inStart; // 左边有几个元素
+            h.left = build(preorder, inorder, preStart + 1, preStart + l, inStart, inS - 1);
+            h.right = build(preorder, inorder, preStart + l + 1, preEnd, inS + 1, inEnd);
+            return h;
+        }
+    }
+
+}
diff --git a/src/main/java/cn/whaifree/redo/redoAll/LeetCode110.java b/src/main/java/cn/whaifree/redo/redoAll/LeetCode110.java
new file mode 100644
index 0000000..db84f05
--- /dev/null
+++ b/src/main/java/cn/whaifree/redo/redoAll/LeetCode110.java
@@ -0,0 +1,42 @@
+package cn.whaifree.redo.redoAll;
+
+import cn.whaifree.leetCode.model.TreeNode;
+import org.junit.Test;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/3/31 12:29
+ * @注释
+ */
+public class LeetCode110{
+
+    @Test
+    public void test()
+    {
+        Solution solution = new Solution();
+        System.out.println(solution.isBalanced(TreeNode.constructTreeByArray(1,2,2,3,null,null,3,4,null,null,4)));
+    }
+
+
+    class Solution {
+        public boolean isBalanced(TreeNode root) {
+            return getLevel(root) != -1;
+        }
+
+        public int getLevel(TreeNode root) {
+            if (root == null) {
+                return 0;
+            }
+            int left = getLevel(root.left);
+            int right = getLevel(root.right);
+            if (left == -1 || right == -1) {
+                return -1;
+            }
+            if (Math.abs(left - right) > 1) {
+                return -1;
+            }
+            return Math.max(left, right) + 1;
+        }
+    }
+}
diff --git a/src/main/java/cn/whaifree/redo/redoAll/LeetCode199.java b/src/main/java/cn/whaifree/redo/redoAll/LeetCode199.java
new file mode 100644
index 0000000..665cd77
--- /dev/null
+++ b/src/main/java/cn/whaifree/redo/redoAll/LeetCode199.java
@@ -0,0 +1,68 @@
+package cn.whaifree.redo.redoAll;
+
+import cn.whaifree.leetCode.model.TreeNode;
+import org.junit.Test;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Deque;
+import java.util.List;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/3/31 11:37
+ * @注释
+ */
+public class LeetCode199 {
+    @Test
+    public void test() {
+
+        Solution1 solution = new Solution1();
+        List<Integer> integers = solution.rightSideView(TreeNode.constructTreeByArray(1, 2, 3, null, 5, null, null));
+        for (int i = 0; i < integers.size(); i++) {
+            System.out.println(integers.get(i));
+        }
+    }
+
+    class Solution {
+        public List<Integer> rightSideView(TreeNode root) {
+            List<Integer> res = new ArrayList<>();
+            if (root == null) {
+                return res;
+            }
+            // 层次遍历，每层的最后一个
+            Deque<TreeNode> queue = new ArrayDeque<>();
+            queue.add(root);
+            while (!queue.isEmpty()) {
+                int size = queue.size();
+                for (int i = 0; i < size ; i++) {
+                    TreeNode e = queue.pop();
+                    if (e.left != null) queue.add(e.left);
+                    if (e.right != null) queue.add(e.right);
+                    if (i == size - 1) {
+                        res.add(e.val);
+                    }
+                }
+
+            }
+            return res;
+        }
+    }
+    class Solution1 {
+        List<Integer> res = new ArrayList<>();
+        public List<Integer> rightSideView(TreeNode root) {
+            level(root, 0);
+            return res;
+        }
+
+        public void level(TreeNode root, int level) {
+            if (root == null) {
+                return;
+            }
+            if (res.size() == level) res.add(root.val);
+            level(root.right, level + 1);
+            level(root.left, level + 1);
+        }
+    }
+}
diff --git a/src/main/java/cn/whaifree/redo/redoAll/LeetCode216.java b/src/main/java/cn/whaifree/redo/redoAll/LeetCode216.java
new file mode 100644
index 0000000..8801d7d
--- /dev/null
+++ b/src/main/java/cn/whaifree/redo/redoAll/LeetCode216.java
@@ -0,0 +1,57 @@
+package cn.whaifree.redo.redoAll;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/3/31 15:51
+ * @注释
+ */
+public class LeetCode216
+{
+
+
+    @Test
+    public void test()
+    {
+        Solution solution = new Solution();
+        List<List<Integer>> lists = solution.combinationSum3(2, 18);
+        System.out.println(lists);
+    }
+
+
+    class Solution {
+
+        List<List<Integer>> res;
+        List<Integer> path;
+        int sum = 0;
+        public List<List<Integer>> combinationSum3(int k, int n) {
+            res = new ArrayList<>();
+            path = new ArrayList<>();
+            backTracking(k, n, 1);
+            return res;
+        }
+
+        public void backTracking(int k, int n, int startIndex)
+        {
+            if (k == path.size() && n == sum) {
+                res.add(new ArrayList<>(path));
+            }
+
+            for (int i = startIndex; i < 10; i++) {
+                if (sum + i > n) {
+                    break;
+                }
+                sum += i;
+                path.add(i);
+                backTracking(k, n, i + 1);
+                sum -= i;
+                path.remove(path.size() - 1);
+            }
+        }
+    }
+}
diff --git a/src/main/java/cn/whaifree/redo/redoAll/LeetCode222.java b/src/main/java/cn/whaifree/redo/redoAll/LeetCode222.java
new file mode 100644
index 0000000..1edf746
--- /dev/null
+++ b/src/main/java/cn/whaifree/redo/redoAll/LeetCode222.java
@@ -0,0 +1,58 @@
+package cn.whaifree.redo.redoAll;
+
+import cn.whaifree.leetCode.model.TreeNode;
+import org.junit.Test;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/3/31 14:57
+ * @注释
+ */
+public class LeetCode222 {
+    @Test
+    public void test() {
+        TreeNode root = TreeNode.constructTreeByArray(1, 2, 3, 4, 5, 6);
+        System.out.println(new Solution().countNodes(root));
+    }
+
+    class Solution {
+        /**
+         * 1. 左右都没有
+         * 2. 左有右没有
+         * @param root
+         * @return
+         */
+        public int countNodes(TreeNode root) {
+
+            // 左边深度
+            // 右边深度
+            // 如果左右边深度不一样，往右边下去找
+            // 如果左右深度一样，直接返回 2<<level - 1
+
+            return cir(root);
+        }
+        public int cir(TreeNode root) {
+            if (root == null) {
+                return 0;
+            }
+            TreeNode leftIndex = root;
+            int leftLevel = 0;
+            while (leftIndex != null) {
+                leftIndex = leftIndex.left;
+                leftLevel++;
+            }
+            TreeNode rightIndex = root;
+            int rightLevel = 0;
+            while (rightIndex != null) {
+                rightIndex = rightIndex.right;
+                rightLevel++;
+            }
+            if (leftLevel != rightLevel) {
+                return cir(root.right) + cir(root.left) + 1;
+            } else {
+                return (2 << (leftLevel - 1)) - 1;
+            }
+        }
+    }
+}
diff --git a/src/main/java/cn/whaifree/redo/redoAll/LeetCode246.java b/src/main/java/cn/whaifree/redo/redoAll/LeetCode246.java
new file mode 100644
index 0000000..9c0c2ec
--- /dev/null
+++ b/src/main/java/cn/whaifree/redo/redoAll/LeetCode246.java
@@ -0,0 +1,54 @@
+package cn.whaifree.redo.redoAll;
+
+import cn.whaifree.leetCode.model.TreeNode;
+import org.junit.Test;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/3/31 15:46
+ * @注释
+ */
+public class LeetCode246 {
+
+    @Test
+    public void test()
+    {
+        TreeNode root = TreeNode.constructTreeByArray(6,2,8,0,4,7,9,null,null,3,5);
+        TreeNode p = new TreeNode(0);
+        TreeNode q = new TreeNode(5);
+        Solution solution = new Solution();
+        TreeNode treeNode = solution.lowestCommonAncestor(root, p, q);
+        System.out.println(treeNode.val);
+    }
+
+    class Solution {
+        public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
+
+            if (root == null) {
+                return null;
+            }
+
+            if (root.val == p.val || root.val == q.val) {
+                return root;
+            }
+
+            TreeNode left = lowestCommonAncestor(root.left, p, q);
+            TreeNode right = lowestCommonAncestor(root.right, p, q);
+
+            if(left == null && right == null){
+                return null;
+            }
+            if (left != null && right != null) {
+                return root;
+            }
+            if (left == null) {
+                return right;
+            }else {
+                return left;
+            }
+
+
+        }
+    }
+}
diff --git a/src/main/java/cn/whaifree/redo/redoAll/LeetCode257.java b/src/main/java/cn/whaifree/redo/redoAll/LeetCode257.java
new file mode 100644
index 0000000..7b6dd9b
--- /dev/null
+++ b/src/main/java/cn/whaifree/redo/redoAll/LeetCode257.java
@@ -0,0 +1,59 @@
+package cn.whaifree.redo.redoAll;
+
+import cn.whaifree.leetCode.model.TreeNode;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/3/31 12:54
+ * @注释
+ */
+public class LeetCode257 {
+    @Test
+    public void test() {
+
+        new Solution().binaryTreePaths(TreeNode.constructTreeByArray(1)).forEach(
+                i -> System.out.println(i)
+        );
+    }
+
+    class Solution {
+
+        List<String> list;
+        List<Integer> path;
+        public List<String> binaryTreePaths(TreeNode root) {
+            list = new ArrayList<>();
+            path = new ArrayList<>();
+            in(root);
+            return list;
+        }
+
+        public void in(TreeNode root) {
+            if (root == null) {
+                return;
+            }
+            if (root.right == null && root.left == null) {
+                // 还有尾巴一个节点要处理
+                StringBuilder stringBuilder = new StringBuilder();
+                path.forEach(i -> {
+                    stringBuilder.append(i).append("->");
+                });
+                stringBuilder.append(root.val);
+                list.add(stringBuilder.toString());
+                return;
+            }
+            path.add(root.val);
+            if (root.left != null) {
+                in(root.left);
+            }
+            if (root.right != null) {
+                in(root.right);
+            }
+            path.remove(path.size() - 1);
+        }
+    }
+}
diff --git a/src/main/java/cn/whaifree/redo/redoAll/LeetCode77.java b/src/main/java/cn/whaifree/redo/redoAll/LeetCode77.java
new file mode 100644
index 0000000..e139940
--- /dev/null
+++ b/src/main/java/cn/whaifree/redo/redoAll/LeetCode77.java
@@ -0,0 +1,57 @@
+package cn.whaifree.redo.redoAll;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @version 1.0
+ * @Author whai文海
+ * @Date 2024/3/31 15:13
+ * @注释
+ */
+public class LeetCode77 {
+
+    @Test
+     public void test()
+     {
+         Solution solution = new Solution();
+         List<List<Integer>> lists = solution.combine(4, 2);
+         System.out.println(lists);
+     }
+
+    class Solution {
+
+        List<Integer> path = new ArrayList<>();
+        List<List<Integer>> res = new ArrayList<>();
+        public List<List<Integer>> combine(int n, int k) {
+            backtrack(n, k, 1);
+            return res;
+        }
+
+        public void backtrack(int n, int k, int startIndex)
+        {
+            if (path.size() == k) {
+                res.add(new ArrayList<>(path));
+                return;
+            }
+//            if (startIndex > n) {
+//                return;
+//            }
+
+            for (int i = startIndex; i <= n; i++) {
+                // 剪枝
+                if (n - startIndex + 1 < k - path.size()) {
+                    return;
+                }
+                path.add(i);
+                backtrack(n, k, i + 1);
+                path.remove(path.size() - 1);
+            }
+
+
+
+        }
+    }
+}