diff --git a/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/dynamic/LC_309_MaxProfit.java b/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/dynamic/LC_309_MaxProfit.java
new file mode 100644
index 0000000..ba21beb
--- /dev/null
+++ b/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/dynamic/LC_309_MaxProfit.java
@@ -0,0 +1,16 @@
+package com.markilue.leecode.hot100.interviewHot.dynamic;
+
+/**
+ *@BelongsProject: Leecode
+ *@BelongsPackage: com.markilue.leecode.hot100.interviewHot.dynamic
+ *@Author: markilue
+ *@CreateTime: 2023-05-31  13:23
+ *@Description: TODO  力扣309  最佳买卖股票时机含冷冻期
+ *@Version: 1.0
+ */
+public class LC_309_MaxProfit {
+
+    public int maxProfit(int[] prices) {
+        return 0;
+    }
+}
diff --git a/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/union_find/second/LC_685_FindRedundantConnection.java b/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/union_find/second/LC_685_FindRedundantConnection.java
new file mode 100644
index 0000000..20e0c32
--- /dev/null
+++ b/Leecode/src/main/java/com/markilue/leecode/hot100/interviewHot/union_find/second/LC_685_FindRedundantConnection.java
@@ -0,0 +1,102 @@
+package com.markilue.leecode.hot100.interviewHot.union_find.second;
+
+import java.util.ArrayList;
+
+/**
+ *@BelongsProject: Leecode
+ *@BelongsPackage: com.markilue.leecode.hot100.interviewHot.union_find.second
+ *@Author: markilue
+ *@CreateTime: 2023-05-31  10:47
+ *@Description: TODO  力扣685  冗余连接II
+ *@Version: 1.0
+ */
+public class LC_685_FindRedundantConnection {
+
+    int[] father;//父节点
+    int n;//父节点个数
+
+    private void init(int[] father) {
+        for (int i = 0; i < father.length; i++) {
+            father[i] = i;
+        }
+    }
+
+    private int find(int u) {
+        if (u == father[u]) {
+            return u;
+        }
+        father[u] = find(father[u]);
+        return father[u];
+    }
+
+    private void join(int u, int v) {
+        u = find(u);
+        v = find(v);
+        if (u == v) return;
+        father[v] = u;
+    }
+
+    private boolean same(int u, int v) {
+        u = find(u);
+        v = find(v);
+        return u == v;
+    }
+
+
+    private boolean isSameAfterRemove(int[][] edges, int delete) {
+        init(father);
+
+        for (int i = 0; i < edges.length; i++) {
+            if (i == delete) {
+                continue;
+            }
+            if (same(edges[i][0], edges[i][1])) {
+                return false;
+            }
+            join(edges[i][0], edges[i][1]);
+        }
+        return true;
+    }
+
+    private int[] removeOne(int[][] edges) {
+        init(father);
+
+        for (int i = 0; i < edges.length; i++) {
+
+            if (same(edges[i][0], edges[i][1])) {
+                return edges[i];
+            }
+            join(edges[i][0], edges[i][1]);
+        }
+        return null;
+    }
+
+
+    public int[] findRedundantDirectedConnection(int[][] edges) {
+        n = 1010;
+        father = new int[n];
+
+        //计算每个节点的入度
+        int[] inDegree = new int[n];
+        for (int[] edge : edges) {
+            inDegree[edge[1]]++;
+        }
+
+        ArrayList<Integer> twoDegree = new ArrayList<>();
+        //判断入度为2的节点，该节点一定有子节点需要删除;反向遍历,因为后面的删除优先级更高
+        for (int i = edges.length-1; i >=0; i--) {
+            if (inDegree[edges[i][1]] == 2) {
+                twoDegree.add(i);//这个节点需要删除
+            }
+        }
+
+        if (!twoDegree.isEmpty()) {
+            if (isSameAfterRemove(edges, twoDegree.get(0))) {
+                return edges[twoDegree.get(0)];
+            }
+            return edges[twoDegree.get(1)];
+        }
+
+        return removeOne(edges);
+    }
+}
diff --git a/Leecode/src/main/java/com/markilue/leecode/hot100/second/T77_297_Codec.java b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T77_297_Codec.java
index 3795046..1e14ac1 100644
--- a/Leecode/src/main/java/com/markilue/leecode/hot100/second/T77_297_Codec.java
+++ b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T77_297_Codec.java
@@ -60,6 +60,7 @@ public class T77_297_Codec {
 
     // Decodes your encoded data to tree.
     public TreeNode deserialize(String data) {
+
         if (in >= data.length() || data.charAt(in) == ')') {
             return null;
         }
@@ -70,7 +71,7 @@ public class T77_297_Codec {
             in++;
         }
 
-        while (in < data.length() && data.charAt(in) >= '0' && data.charAt(in) <= '9') {
+        while (in < data.length() && Character.isDigit(data.charAt(in))) {
             root.val = root.val * 10 + data.charAt(in)-'0';
             in++;
         }
diff --git a/Leecode/src/main/java/com/markilue/leecode/hot100/second/T78_300_LengthOfLIS.java b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T78_300_LengthOfLIS.java
new file mode 100644
index 0000000..5139c2b
--- /dev/null
+++ b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T78_300_LengthOfLIS.java
@@ -0,0 +1,50 @@
+package com.markilue.leecode.hot100.second;
+
+import org.junit.Test;
+
+import java.util.ArrayDeque;
+
+/**
+ *@BelongsProject: Leecode
+ *@BelongsPackage: com.markilue.leecode.hot100.second
+ *@Author: markilue
+ *@CreateTime: 2023-05-31  11:18
+ *@Description: TODO  力扣300  最长递增子序列
+ *@Version: 1.0
+ */
+public class T78_300_LengthOfLIS {
+
+    @Test
+    public void test() {
+//        int[] nums ={10,9,2,5,3,7,101,18};
+        int[] nums = {0, 1, 0, 3, 2, 3};
+        System.out.println(lengthOfLIS(nums));
+    }
+
+
+    //构造一个单调栈:存放位置，核心问题在于子序列，所以动态规划不合适
+    //单调栈不合适,因为pop出的数字可能还有用
+    public int lengthOfLIS(int[] nums) {
+
+        int[] stack = new int[nums.length];
+        int index = 0;
+        stack[index] = nums[0];
+
+
+        for (int i = 1; i < nums.length; i++) {
+            if (stack[index] < nums[i]) {
+                stack[++index] = nums[i];
+            } else {
+                //找出第一个比他小的位置,并替代
+                for (int j = 0; j <= index; j++) {
+                    if (stack[j] >= nums[i]) {
+                        stack[j] = nums[i];
+                        break;
+                    }
+                }
+            }
+        }
+
+        return index+1;
+    }
+}
diff --git a/Leecode/src/main/java/com/markilue/leecode/hot100/second/T79_301_RemoveInvalidParentheses.java b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T79_301_RemoveInvalidParentheses.java
new file mode 100644
index 0000000..3909df0
--- /dev/null
+++ b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T79_301_RemoveInvalidParentheses.java
@@ -0,0 +1,87 @@
+package com.markilue.leecode.hot100.second;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ *@BelongsProject: Leecode
+ *@BelongsPackage: com.markilue.leecode.hot100.second
+ *@Author: markilue
+ *@CreateTime: 2023-05-31  11:50
+ *@Description: TODO  力扣301  删除无效的括号
+ *@Version: 1.0
+ */
+public class T79_301_RemoveInvalidParentheses {
+
+    @Test
+    public void test() {
+        String s = "(a)())()";
+        System.out.println(removeInvalidParentheses(s));
+    }
+
+
+    //朴素的想法:判断左右括号哪个多，确定删除谁;然后挨个删，最后通过判断合不合适来加入结果
+    public List<String> removeInvalidParentheses(String s) {
+
+        int left = 0;
+        int right = 0;
+
+        for (int i = 0; i < s.length(); i++) {
+            if (s.charAt(i) == '(') {
+                left++;
+            } else if (s.charAt(i) == ')') {
+                if (left > 0) {
+                    left--;
+                } else {
+                    right++;
+                }
+            }
+        }
+        List<String> result = new ArrayList<>();
+        removeHelper(s, left, right, result,0);
+        return result;
+
+    }
+
+    //需要注意这个start；一定要从这个字母后面开始删除
+    public void removeHelper(String s, int left, int right, List<String> res,int start) {
+        if (left == 0 && right == 0) {
+            if (isValid(s)) {
+                res.add(new String(s));
+            }
+            return;
+        }
+
+        for (int i = start; i < s.length(); i++) {
+            if (i > 0 && s.charAt(i) == s.charAt(i - 1)) continue;//去重
+            if (left + right > s.length() - i) {
+                //怎么删都不够了
+                return;
+            }
+            if (left > 0 && s.charAt(i) == '(') {
+                removeHelper(s.substring(0, i) + s.substring(i + 1), left - 1, right, res,i);
+            }
+            if (right > 0 && s.charAt(i) == ')') {
+                removeHelper(s.substring(0, i) + s.substring(i + 1), left, right - 1, res,i);
+            }
+        }
+
+    }
+
+    private boolean isValid(String s) {
+        int left = 0;
+        for (int i = 0; i < s.length(); i++) {
+            if (s.charAt(i) == '(') {
+                left++;
+            } else if (s.charAt(i) == ')') {
+                left--;
+                if (left < 0) return false;
+            }
+        }
+        return true;
+    }
+
+
+}
diff --git a/Leecode/src/main/java/com/markilue/leecode/hot100/second/T80_309_MaxProfit.java b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T80_309_MaxProfit.java
new file mode 100644
index 0000000..1db8ff8
--- /dev/null
+++ b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T80_309_MaxProfit.java
@@ -0,0 +1,39 @@
+package com.markilue.leecode.hot100.second;
+
+/**
+ *@BelongsProject: Leecode
+ *@BelongsPackage: com.markilue.leecode.hot100.second
+ *@Author: markilue
+ *@CreateTime: 2023-05-31  13:22
+ *@Description: TODO  力扣309  最佳买卖股票时机含冷冻期
+ *@Version: 1.0
+ */
+public class T80_309_MaxProfit {
+
+    /**
+     * 动态规划:
+     *   状态分为：
+     *      1.今天没有股票(不在冷冻期)
+     *      2.今天没有股票(在冷冻期)  ->刚刚卖出
+     *      3.今天买了股票
+     * @param prices
+     * @return
+     */
+    public int maxProfit(int[] prices) {
+
+        //对应状态1  2  3
+        int dp0 = 0;
+        int dp1 = 0;
+        int dp2 = -prices[0];
+        int temp;
+        for (int i = 0; i < prices.length; i++) {
+            temp = dp0;
+            dp0 = Math.max(dp0, dp1);//昨天就没买股票;昨天在冷冻期
+            dp1 = dp2 + prices[i];//昨天有股票,今天卖了
+            dp2 = Math.max(dp2, temp - prices[i]);//昨天有股票；昨天没股票且不再冷冻期，今天买了
+        }
+
+        return Math.max(dp0, dp1);
+
+    }
+}