A common problem (before learning it is impossible/fraught with danger) is categorisation, like sorting of strings.

Say you have a text, and need to count words of different lengths.

One intuitive approach is to pass through it once and add each word to a list for the corresponding length, as well as making lists as needed. No 7 letter words, no 7-letter-word-list, even though there are longer words.

As humans we're good at sorting things into an unknown number of categories, and we have to unlearn that for programming