Add Two Numbers, two ways

Try:
CALL
1 / 1

Code

The highlighted line runs next. The pill shows the live values in the running call.

Cost

Work done so far, and how the two solutions compare

Digits by place value

The highlighted column is being added

Keyboard: ← → step, Space play or pause. 1 to 6 digits per list, ones digit first, no leading zeros. Java and C++ use the ListNode(val, next) constructor that LeetCode provides.