Add digit by digit with carry, like elementary addition.
Traverse both lists simultaneously. Sum current digits and carry, create a new node for sum % 10, update carry.
The lists represent numbers in reverse order, so least significant digits come first, matching left-to-right traversal.
Add digit by digit with carry, like elementary addition.
Traverse both lists simultaneously. Sum current digits and carry, create a new node for sum % 10, update carry.
The lists represent numbers in reverse order, so least significant digits come first, matching left-to-right traversal.