add Python 23,24,25,26 solutions

Author: qinyii

Problems/23-Partition-Array-for-Maximum-Sum/Partition_Array_for_Max_Sum.py

@@ -0,0 +1,21 @@
+class Solution(object):
+    def maxSumAfterPartitioning(self, arr, k):
+        """
+        :type arr: List[int]
+        :type k: int
+        :rtype: int
+        """
+        n = len(arr)
+        res = [0] * (n+1)
+
+        for i in range(1, n+1):
+            max_val = 0
+            for j in range(1, k+1):
+                pos = i - j
+                if pos < 0:
+                    break
+                if arr[pos] > max_val:
+                    max_val = arr[pos]
+                res[i] = max(res[i], max_val * j + res[pos])
+        return res[-1]
+       

Problems/24-Where-Will-the-Ball-Fall/Where-Will-the-Ball-Fall.py

@@ -0,0 +1,26 @@
+class Solution(object):
+    def findBall(self, grid):
+        """
+        :type grid: List[List[int]]
+        :rtype: List[int]
+        """
+        n = len(grid[0])
+        ans = [-1] * n
+        for i in range(n):
+            col = i 
+            print(col) 
+            for row in grid:
+                dir = row[col]
+                col += dir 
+                if col < 0 or col == n or row[col] != dir: 
+                    break
+            else:  
+                ans[i] = col
+        return ans
+              
+               
+   
+                    
+           
+grid = [[1,1,1,-1,-1],[1,1,1,-1,-1],[-1,-1,-1,1,1],[1,1,1,1,-1],[-1,-1,-1,-1,-1]]
+print(Solution().findBall(grid))

Problems/25-Flip-String-to-Monotone-Increasing/Flip-String-to-Monotone-Increasing.py

@@ -0,0 +1,17 @@
+class Solution(object):
+    def minFlipsMonoIncr(self, s):
+        """
+        :type s: str
+        :rtype: int
+        """
+        
+        #使得该分界点之前1的个数和分界点之后0的个数之和最小，把分界点之前的1变成0，之后的0变成1
+        m=s.count('0')  
+        res=[m]
+        for x in s:
+            if x=='1':  
+                m+=1
+            else:       
+                m-=1
+                res.append(m)        
+        return min(res)

Problems/26-Knight-Dialer/Knight-Dialer.py

@@ -0,0 +1,18 @@
+class Solution(object):
+    def knightDialer(self, n):
+        """
+        :type n: int
+        :rtype: int
+        """
+        if n==1: 
+            return 10
+        #A:{1,3,7,9}, B:{2,8}, C:{4,6}, D:{0}
+        # 处于状态A中的数字(1,3,7,9)通过一次跳跃要么变成状态B(2,8)，要么变成状态C(4,6)
+        # 处于状态B中的数字(2,8)通过一次跳跃有两种方式变成状态A(1,3,7,9)
+        # 处于状态C中的数字(4,6)通过一次跳跃有两种方式变成状态A(1,3,7,9)，还有一种方式变成状态D(0)
+        # 处于状态D中的数字(0)通过一次跳跃有两种方式变成状态C(4,6)
+
+        nums=[1,1,1,1]
+        for _ in range(n-1):
+            nums=[nums[1]+nums[2], 2*nums[0], 2*nums[0]+nums[3], 2*nums[2]]       
+        return (4*nums[0]+2*nums[1]+2*nums[2]+nums[3])%1000000007