To transform string 'ca' to 'a', I don't understand why the answer is '1, S' (1, substitution) instead of '1, D' (1, deletion).
Since 'a' == 'a', then shouldn't we use the diagonal cell, which is '1, D' ? The instruction says it himself: "so there are actually no substitutions that need to happen".
I'm confused. Thanks in advance.
link to the video: https://youtu.be/YTO92oVoYwA?t=7m43s