diff --git a/Week_02/id_15/LeetCode_1_015.py b/Week_02/id_15/LeetCode_1_015.py
new file mode 100644
index 00000000..ee5d6dd2
--- /dev/null
+++ b/Week_02/id_15/LeetCode_1_015.py
@@ -0,0 +1,7 @@
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        d={}
+        for i,num in enumerate(nums):
+            if target-num in d:
+                return d[target-num], i
+            d[num]=i
diff --git a/Week_02/id_15/LeetCode_242_015.py b/Week_02/id_15/LeetCode_242_015.py
new file mode 100644
index 00000000..b89088ca
--- /dev/null
+++ b/Week_02/id_15/LeetCode_242_015.py
@@ -0,0 +1,14 @@
+class Solution:
+    def isAnagram(self, s: str, t: str) -> bool:
+        if s =="" and t == "":
+            return True
+        
+        if len(s) != len(t) or len(set(s)) != len(set(t)):
+            return False
+        
+        for char in set(s):
+            s_count = s.count(char)
+            t_count = t.count(char)
+            if s_count != t_count:
+                return False
+        return True
diff --git a/Week_02/id_15/LeetCode_3_015.py b/Week_02/id_15/LeetCode_3_015.py
new file mode 100644
index 00000000..84c04c27
--- /dev/null
+++ b/Week_02/id_15/LeetCode_3_015.py
@@ -0,0 +1,12 @@
+class Solution:
+    def lengthOfLongestSubstring(self, s: str) -> int:
+        substring, length, max_len = "", 0, 0
+        for c in s:
+            if c in substring:
+                index = substring.find(c)
+                substring = substring[(index + 1)::]
+            substring += c
+            length = len(substring)
+            if length > max_len:
+                max_len = length
+        return max_len
diff --git a/Week_02/id_15/NOTE.md b/Week_02/id_15/NOTE.md
index 107ea7d6..820d3a2c 100644
--- a/Week_02/id_15/NOTE.md
+++ b/Week_02/id_15/NOTE.md
@@ -1 +1,11 @@
 # 学习笔记
+## 日常计划
+ - 完成相对应的算法习题
+
+## 算法相关书籍
+ - 任务：完成数据结构与算法Python语言描述阅读
+ - 心得：这本书完全第一遍刷下来以后发现不是非常入门的深度，比上本图解的书难很多。不少地方都需要听下来思考，收获是更加深入的了解了Python这个语言背后的一些数据结构与算法的实现原理。比如内置函数Sort()背后的算法是依据Tim算法来实现的，再比如如果要调用Python实现堆栈，可以考虑用deque这个数据结构。
+ 
+## 下周计划
+ - 复刷之前做过的算法题和尚未完成的新题
+ - 完成新一周的算法作业
diff --git a/Week_03/id_15/LeetCode_200_015.py b/Week_03/id_15/LeetCode_200_015.py
new file mode 100644
index 00000000..284862b6
--- /dev/null
+++ b/Week_03/id_15/LeetCode_200_015.py
@@ -0,0 +1,26 @@
+class Solution:
+    def numIslands(self, grid: List[List[str]]) -> int:
+        num_islands = 0
+    
+        for row in range(len(grid)):
+            for column in range(len(grid[0])):
+                if grid[row][column] == '1':
+                    num_islands += 1
+                    self.island_dfs(grid, row, column)
+        
+        return num_islands
+    
+    def island_dfs(self, grid, row, column):
+        min_row, max_row = 0, len(grid) - 1
+        min_column, max_column = 0, len(grid[0]) - 1
+        
+        if (not min_row <= row <= max_row) or (not min_column <= column <= max_column):
+            return
+        elif grid[row][column] != '1':
+            return
+        else:
+            grid[row][column] = '0'
+            self.island_dfs(grid, row-1, column)
+            self.island_dfs(grid, row+1, column)
+            self.island_dfs(grid, row, column-1)
+            self.island_dfs(grid, row, column+1)
diff --git a/Week_03/id_15/LeetCode_210_015.py b/Week_03/id_15/LeetCode_210_015.py
new file mode 100644
index 00000000..56b76a57
--- /dev/null
+++ b/Week_03/id_15/LeetCode_210_015.py
@@ -0,0 +1,33 @@
+class Solution:
+    def dfs(self, n, g, flags, seqs):
+        if flags[n] == 0: return False
+        if flags[n] == 1: return True
+        
+        flags[n] = 0
+        for m in g[n]:
+            if not self.dfs(m,g,flags,seqs): return False
+        flags[n] = 1
+        seqs.append(n)
+        return True
+    
+    def findOrder(self, numCourses, prerequisites):
+        """
+        :type numCourses: int
+        :type prerequisites: List[List[int]]
+        :rtype: List[int]
+        """
+        
+        g = [[] for _ in range(numCourses)]
+        for b,a in prerequisites:
+            g[a].append(b)
+        
+		# -1: not visited
+		# 0: visiting
+		# 1: visited
+        flags = [-1]*numCourses
+        seqs = []
+        for i in range(numCourses):
+            if not self.dfs(i,g,flags,seqs): return []
+        
+        seqs = seqs[::-1]
+        return seqs
diff --git a/Week_03/id_15/NOTE.md b/Week_03/id_15/NOTE.md
index 107ea7d6..f1e5a245 100644
--- a/Week_03/id_15/NOTE.md
+++ b/Week_03/id_15/NOTE.md
@@ -1 +1,19 @@
 # 学习笔记
+
+## 日常计划
+ - 完成相对应的算法习题
+
+## 心得交流
+ - 本周和小组同学一起线下交流了一整个下午，大家非常认真的梳理了数据结构和算法的基本知识脉络。
+ - 除了算法以外的分享外，同学们还给讲解了开发一般流程，记录如下：
+  - 需求沟通：产品经理与需求提出方进行需求沟通与分析，明确任务
+  - 可行性分析：产品经理与程序员沟通，敲定可行性以及具体的使用语言与框架
+  - 程序开发：
+    - 数据库人员建ER关系图
+    - 开发人员进行程序开发
+  - 程序测试
+  - 产品交付与持续迭代
+ 
+## 下周计划
+ - 复刷之前做过的算法题和尚未完成的新题
+ - 完成新一周的算法作业