diff --git a/leetcode/1. two sum class.py b/leetcode/1. two sum class.py
new file mode 100644
index 0000000..536337c
--- /dev/null
+++ b/leetcode/1. two sum class.py	
@@ -0,0 +1,36 @@
+"""
+# LeetCode
+# 1. Two Sum
+
+Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.
+
+You may assume that each input would have exactly one solution, and you may not use the same element twice.
+
+You can return the answer in any order.
+
+ 
+
+"""
+class Solution():
+    def __init__(self, nums, target):
+        self.nums=nums 
+        self.target=target
+        
+    def twoSum(self, nums, target):        
+        d = {} # dictionary
+        for i in range(len(nums)):
+            num1 = nums[i]
+            num2 = target - num1
+            print("d1=",d)
+            if num2 in d:
+
+                return [d[num2], i]
+            d[num1] = i
+            
+sol = Solution([8,5], 13) # 類別 給值 命名sol
+print(sol.twoSum([20,8,8,40,50,5,80], 13)) # sol 內的twoSum
+
+"""
+# print("num1=",num1)  =8
+# print("num2= 13-5 =",num2)
+"""
\ No newline at end of file
diff --git a/leetcode/1. two sum.py b/leetcode/1. two sum.py
new file mode 100644
index 0000000..71a8fba
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+++ b/leetcode/1. two sum.py	
@@ -0,0 +1,42 @@
+"""
+# LeetCode
+# 1. Two Sum
+
+# num1 + num2 = target 
+https://ithelp.ithome.com.tw/articles/10269246
+
+此題有  class Solution(object):
+    須再學習
+"""
+
+def twoSum(nums, target):
+    d = {}
+    for i in range(len(nums)):
+        print("i=",i)
+        num1 = nums[i]
+        num2 = target - num1 # 5有重複
+        if num2 in d: 
+            print("num2=",num2)
+            print("num1=",num1)
+
+            return [d[num2], i]
+        d[num1] = i
+        print("d[num1]=",i)
+
+twoSum([3,8,8,2,5,4], 13)
+
+# <法二>
+# def twoSum( nums, target):
+#     i = 0
+#     j = len(nums) - 1
+    
+#     while (nums[i] + nums[j] != target):
+#         if (nums[i] + nums[j] > target):
+#             j = j - 1
+#         else:
+#             i = i + 1
+#             # print("i=",i,"j=",j)    
+#     return [i, j]
+
+# twoSum([2,3,4,5,8,8], 13)
+# 此法需排序
diff --git a/leetcode/13. romanToInt.py b/leetcode/13. romanToInt.py
new file mode 100644
index 0000000..b61879e
--- /dev/null
+++ b/leetcode/13. romanToInt.py	
@@ -0,0 +1,83 @@
+"""
+13. Roman to Integer
+
+I             1
+V             5
+X             10
+L             50
+C             100
+D             500
+M             1000
+
+"""
+
+class Solution(object):
+    def __init__(self, s):
+        self.s = s
+    def romanToInt(self, s):
+
+        d = {'I':1, 'V':5, 'X':10, 'L':50, 'C':100, 'D':500, 'M':1000}
+        result = 0
+        
+        for i in range (len(s)):
+
+            if i >0 and d[ s[i] ] > d[ s[i-1] ]:        
+                result += d[ s[i] ] -2* d[ s[i-1] ]
+
+            else:
+                result += d[ s[i] ] 
+        return  result
+
+
+
+n = Solution("MCMXCIV")
+print("n=", n.romanToInt("MCMXCIV"))
+
+"""
+MC = 1000+100 = 1100
+CM = 1000-100 = 900
+MCM = 1900 = 1000+100 -100*2
+MX = 10
+MCMX = 1910
+XC = 100-10*2 (MCMX +XC -X )
+MCMXC = 1990
+CI
+MCMXCI
+IV
+
+
+
+
+class Solution(object):
+    def __init__(self, s):
+        self.s = s
+    def romanToInt(self, s):
+
+        d = {'I':1, 'V':5, 'X':10, 'L':50, 'C':100, 'D':500, 'M':1000}
+        result = 0
+        
+        for i in range (len(s)):
+            
+            print("i=",i)
+            if i >0 and d[ s[i] ] > d[ s[i-1] ]:
+                print("s[i] _1 = ",s[i])
+                print("d[ s[i] ]=",d[ s[i] ])  
+                print("d[ s[i-1]]=",d[ s[i-1] ])                  
+                print("result_1=",result)
+                
+                result += d[ s[i] ] -2* d[ s[i-1] ]
+                print("result_2=",result,"\n")
+            else:
+                print("s[i] _2 = ",s[i])
+
+                result += d[ s[i] ] 
+                print("result_3=",result,"\n")
+        return  result
+
+"""
+
+
+
+
+
+
diff --git a/leetcode/14. Longest Common Prefix.py b/leetcode/14. Longest Common Prefix.py
new file mode 100644
index 0000000..5bd8800
--- /dev/null
+++ b/leetcode/14. Longest Common Prefix.py	
@@ -0,0 +1,42 @@
+"""
+# leetcode
+# 14. Longest Common Prefix
+
+strs[0]  => flower
+strs[1:] => ['flow', 'flight']
+
+"""
+def longestCommonPrefix(strs):
+
+        for i in range( len(strs[0]) ): # 第一個單字的長度
+            for string in strs[1:]:     # 第1個~end
+                if i >= len(string) or string[i] != strs[0][i]:
+                                        # 當i>比較字串長度 或 flower 比較到字母不同 回傳到當下字母
+                    return strs[0][:i]
+        return strs[0]                  # 檢查 strs=[""] 時 不回傳null 需回傳"" 也就是第一個[""]
+    
+strs = ["flower","flow","flight"]
+#strs= [""]
+longestCommonPrefix(strs)
+
+
+
+
+
+
+
+
+
+
+
+#　有 print 版
+# def longestCommonPrefix(strs):
+#     for i in range( len(strs[0]) ): # 第一個單字的長度
+#         print("i = ",i)
+
+#         for string in strs[1:]:     # 第1個~end
+#             if i >= len(string) or string[i] != strs[0][i]:
+#                 print("strs[0][:i] = ",strs[0][:i])
+#                 return strs[0][:i]
+#     print("strs[0] = ",strs[0])
+
diff --git a/leetcode/20. Valid Parentheses.py b/leetcode/20. Valid Parentheses.py
new file mode 100644
index 0000000..8862500
--- /dev/null
+++ b/leetcode/20. Valid Parentheses.py	
@@ -0,0 +1,35 @@
+"""
+# leetcode
+# 20. Valid Parentheses
+
+"{[]}" => true
+
+"""
+
+class Solution(object):
+    def isValid(self, s):
+       
+        lookup = {"(":")", "[":"]", "{":"}" } # 字典
+        stack = [] # 堆疊
+        for bracket in s:
+            if bracket in lookup:
+                stack.append( bracket )
+                
+            # 當pop() 最後一個 "(" 沒有對應 ")"
+            elif len(stack) == 0 or lookup[stack.pop()] != bracket:
+
+                return False 
+            
+        # s ="]" 不合if 所以 len(stack) == 0
+        return len(stack) == 0
+
+n = Solution("({}[])")
+n.isValid("({}[])") 
+
+"""
+corresponding 對應
+Valid         有效的 
+parentheses   圓括號
+Open brackets   => (
+closing bracket =>  )
+"""
\ No newline at end of file
diff --git a/leetcode/21. Merge Two Sorted Lists.py b/leetcode/21. Merge Two Sorted Lists.py
new file mode 100644
index 0000000..fe3a7ee
--- /dev/null
+++ b/leetcode/21. Merge Two Sorted Lists.py	
@@ -0,0 +1,44 @@
+"""
+# leetcode
+# 21. Merge Two Sorted Lists
+
+list1 = [1,2,4]
+list2 = [1,3,4]
+
+Output: [1,1,2,3,4,4]
+
+Merge the two lists in a one sorted list.
+"""
+
+class ListNode(object):
+    def __init__(self, val=0, next=None):
+        self.val = val 
+        self.next = next
+class Solution(object):
+    def mergeTwoLists(self, L1, L2):
+        curr = dummy = ListNode(0) # curr current dummy 虛擬
+        
+        # val有文字有數字 只轉數字
+        while  L1 and  L2:
+            if  L1.val <  L2.val:  
+                     curr.next = L1 # next 返回下一個輸入行
+                     L1 = L1.next
+            else:
+                curr.next = L2
+                L2=  L2.next
+            curr =  curr.next
+        curr.next =  L1 or  L2 # L1結束 接 L2
+        return dummy.next
+    
+n=  ListNode( [1,2,4], [1,3,4])
+print(n.val)
+print(n.next)
+
+        
+        
+        
+        
+        
+        
+        
+
diff --git a/leetcode/7. Reverse Integer.py b/leetcode/7. Reverse Integer.py
new file mode 100644
index 0000000..fa323b2
--- /dev/null
+++ b/leetcode/7. Reverse Integer.py	
@@ -0,0 +1,49 @@
+"""
+# LeetCode
+# 7. Reverse Integer
+
+"""
+class Solution(object):
+    
+    def __init__(self, x):
+        self.x= x
+
+    def reverse(self, x):
+        a = abs(x) 
+        num = 0 
+
+        # abs return an absolute value of number
+        # while迴圈 執行直到 a = 0
+        while (a != 0):
+            temp = a % 10
+            print("a=",a)
+
+            num = num*10 + temp
+            print("temp=",temp)
+
+            print("num=",num)
+            a = a//10
+            # a = int (a/10) 
+
+    
+        if x>0 and num < 2147483647:
+            print("a=",a)
+            return num
+        elif x<0 and num < 2147483648:
+            return -num
+        else:
+            return 0
+            
+num = Solution(12321) 
+print("rev=",num.reverse(12321))
+
+
+"""
+# if x = 12321
+# a = 1232, num = 1 
+# temp = 2(餘數)
+# num = 10+2 =12
+# a = 123, num = 12 
+# temp = 3(餘數)
+# num = 120 +3
+"""
\ No newline at end of file
diff --git a/leetcode/9. Palindrome.py b/leetcode/9. Palindrome.py
new file mode 100644
index 0000000..602fb50
--- /dev/null
+++ b/leetcode/9. Palindrome.py	
@@ -0,0 +1,34 @@
+"""
+# LeetCode
+# 9. Palindrome
+
+"""
+class Solution(object):
+    def __init__(self, x):
+        self.x=x
+    def isPalindrome(self, x):
+        a = abs(x) 
+        num = 0 
+
+        while (a != 0):
+            temp = a % 10
+            num = num*10 + temp
+            a = a//10 
+            # a = int (a/10) 
+    
+        if num ==x and x>=0 and num < 2147483647:
+            return True
+            return num
+        elif num !=x and x<0 and num < 2147483648:
+            return False
+        else:
+            return False
+        
+n = Solution(0)
+print(n.isPalindrome(0))
+
+# x = 0
+# x = 10
+# x = 121
+
+