2020-03-08

Author: JiayangWu

0121.买卖股票的最佳时机/0121-买卖股票的最佳时机.py

@@ -4,24 +4,9 @@ def maxProfit(self, prices):
         :type prices: List[int]
         :rtype: int
         """
-#         dp[i][k][0] = max(dp[i ¨C 1][k][0], dp[I ¨C 1][k][1] + prices[i])
-#         dp[i][k][1] = max(dp[i - 1][k][1], dp[i - 1][k][0] - prices[i])
-#         µÚÒ»Ìâ k = 1
-
-#         dp[i][0] = max(dp[i - 1][0], dp[i - 1][1] + prices[i])
-#         dp[i][1] = max(dp[i - 1][1], dp[i - 1][0] - prices[i])
-
-#         µ±i = 0ʱ£¬
-#         dp[0][0] = 0
-#         dp[0][1] = -prices[0]
-        dp = [[0 for _ in range(2)] for _ in range(len(prices))]
-        for i, price in enumerate(prices):
-            if i == 0:
-                dp[0][0] = 0
-                dp[0][1] = -price
-            else:
-                dp[i][0] = max(dp[i - 1][0], dp[i - 1][1] + prices[i])
-                dp[i][1] = max(dp[i - 1][1],  - prices[i])
-                
-        return dp[len(prices) - 1][0] if prices else 0
-            
+        res = 0
+        pre_min = prices[0] if prices else 0
+        for price in prices:
+            res = max(res, price - pre_min)
+            pre_min = min(pre_min, price)
+        return res

面试题58-II.左旋转字符串/面试题58-II-左旋转字符串.py

@@ -0,0 +1,8 @@
+class Solution(object):
+    def reverseLeftWords(self, s, n):
+        """
+        :type s: str
+        :type n: int
+        :rtype: str
+        """
+        return s[n:] + s[:n]

面试题63.股票的最大利润/面试题63-股票的最大利润.py

@@ -0,0 +1,12 @@
+class Solution(object):
+    def maxProfit(self, prices):
+        """
+        :type prices: List[int]
+        :rtype: int
+        """
+        res = 0
+        pre_min = prices[0] if prices else 0
+        for price in prices:
+            res = max(res, price - pre_min)
+            pre_min = min(pre_min, price)
+        return res

面试题64.求1+2+…+n/面试题64-求1+2+…+n.py

@@ -0,0 +1,7 @@
+class Solution(object):
+    def sumNums(self, n):
+        """
+        :type n: int
+        :rtype: int
+        """
+        return sum(range(1, n + 1))

面试题65.不用加减乘除做加法/面试题65-不用加减乘除做加法.py

@@ -0,0 +1,8 @@
+class Solution(object):
+    def add(self, a, b):
+        """
+        :type a: int
+        :type b: int
+        :rtype: int
+        """
+        return sum([a, b])

面试题66.构建乘积数组/面试题66-构建乘积数组.py

@@ -0,0 +1,16 @@
+class Solution(object):
+    def constructArr(self, a):
+        """
+        :type a: List[int]
+        :rtype: List[int]
+        """
+        left = [1 for _ in a]
+        right = [1 for _ in a]
+        for i in range(1, len(a)):
+            left[i] = left[i - 1] * a[i - 1]
+            
+        for i in range(len(a) - 2, -1, -1):
+            right[i] = right[i + 1] * a[i + 1]
+        
+        return [left[i] * right[i] for i in range(len(a))]
+