L2 | style Tensor+Autograd library | Machine Learning library

In pandas you can do groupby with pd.crosstab

This will work:

Get the index of columns with substring L1 to L3 using grep. Extract the columns, multiply with the value 0.1343109 and update by assigning back to the columns. (Note - multiplying by 1 returns the same value, thus it is left as such)

The reason for the error is that you cannot assume that both prev and prev2 are not None. Your while condition only guarantees that at least one of them is not None, but not both. So that means you still need to have a None check inside the body of the loop.

There are also some other issues:

• l1==[0]: is not correct. The left side of this comparison is a linked list instance, while the right side is a standard list. These comparisons will always be False, and so you can just omit them

• You are adding the carry to the wrong sum. You should add the carry from the previous iteration to the current sum, so things are currently happing in the wrong order.

• The resulting list should be reversed. You can do this on the fly by prefixing each node to l3, instead of appending it. This will also make it unnecessary to create a dummy ListNode(0) before the final loop. You can just start with None.

• Your code mutates the original input lists. This will be acceptable on code challenge sites, and be efficient, but it is bad practice. The caller should not be unpleasantly surprised that the lists they provide as input have been reversed by a call to this addTwoNumbers function. You can solve this in several ways, but it is probably easiest to reverse them a second time to undo that operation.

• To avoid repetition of code, you should create a reverse function

I'll assume that the ListNode constructor can take a second argument for initialising its next reference:

The function week_no is not vectorised so you would need some kind of loop to iterate over each value after strsplit. In the for loop you use sapply, so we can use the same here.

I suggest first create MultiIndex in columns by header=[0,1] by convert first 2 headers rows:

Probably you need something like this:

You need to restrict the ranges for the uppercase and lowercase characters by specifying a lower limit and a higher limit, not just the one value (96) that your current code uses.

Uppercase characters [A,Z] are in [65,90]
Lowercase characters [a,z] are in [97,122]

The nice thing of course is that you don't actually need to write these numbers in your code. You can just write the relevant characters and the assembler will substitute them for you: