python列表切片有~这种简单表示.
class Solution(object): def flipAndInvertImage(self, A): for row in A: for i in xrange((len(row) + 1) / 2): """ In Python, the shortcut row[~i] = row[-i-1] = row[len(row) - 1 - i] helps us find the i-th value of the row, counting from the right. """ row[i], row[~i] = row[~i] ^ 1, row[i] ^ 1 return A