867.转置矩阵

class Solution:
    def transpose(self, A): 
        A[::] = zip(*A)
        return A
    
    def transpose1(self, A): 
        if len(A) == 0: return []
        r, c = len(A), len(A[0])
        return [[A[i][j] for i in range(r)] for j in range(c)]
 

if __name__ == '__main__':
    solu = Solution()
    A = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
    print(solu.transpose(A))

三个数的最大乘积

nums = sorted(nums)
return max(nums[-1]*nums[-2]*nums[-3],nums[-1]*nums[0]*nums[1])

数组中的众数

c=collections.Counter(nums)
return c.most_common(1)[0][0]

切片的知识补充

A=[i for i in range(100)]
A[:10]   #前10
A[-10:]  #后10
A[10:20] #前11-20
A[:10:2] #前10，每2个取一个值
A[::5]   #所有数，每5个取一个值
B=A[:]   #原样复制一个list

单调数列

class Solution:
    def isMonotonic(self, A):
    
        n=len(A)
        count1=0
        count2=0
        for i in range(1,n):
            tmp = A[i-1] - A[i]
            if tmp >=0:
                count1+=1
            if tmp <=0:
                count2+=1
        if count1==n-1 or count2==n-1:
            return True
        else:
            return False

方法二

B=sorted(A)
C=sorted(A,reverse=True)
if A==B or A==C:
     return True
 else:
     return False