leetcode977 Squares of a Sorted Array

"""
Given an array of integers A sorted in non-decreasing order, return an array of the squares of each number, also in sorted non-decreasing order.
Example 1:
Input: [-4,-1,0,3,10]
Output: [0,1,9,16,100]
Example 2:
Input: [-7,-3,2,3,11]
Output: [4,9,9,49,121]
"""
"""
注意观察序列，绝对值大的都在两端
所以可以用头尾两个指针进行遍历
"""
class Solution1:
    def sortedSquares(self, A):
        res = [0]*len(A)
        i, j = 0, len(A)-1
        for k in range(j, -1, -1): #！！！注意这里的写法第二个为-1，区间是[len(A)-1, 0]
            if abs(A[i]) > abs(A[j]):
                res[k] = A[i]**2
                i += 1
            else:
                res[k] = A[j]**2
                j -= 1
        return res
"""
解法二：sorted函数
"""
class Solution2:
    def sortedSquares(self, A):
        return sorted(i**2 for i in A)