Is the word vi the same in Brazilian and European Portuguese?

Yes

The word "vi" is the first-person singular preterite (past tense) of the verb ver (to see). There are no differences in its meaning, spelling, or grammatical function between Brazilian and Continental Portuguese. The only difference is in pronunciation, specifically the phonetic realization of the vowel and the prosody (the rhythm and stress) of the word, which varies according to the respective regional accents.

Brazilian Portuguese Examples

1. Eu vi você na rua ontem. (I saw you on the street yesterday.)
2. Vi esse filme no cinema. (I saw this movie at the cinema.)
3. Eu vi ele no shopping. (I saw him at the mall.)
4. Vi que você esqueceu o celular. (I saw that you forgot your cell phone.)
5. Eu vi o cachorro correndo na rua. (I saw the dog running in the street.)

Portuguese (Continental) Examples

1. Eu vi-te na rua ontem. (I saw you on the street yesterday.)
2. Vi esse filme no cinema. (I saw this movie at the cinema.)
3. Eu vi-o no shopping. (I saw him at the mall.)
4. Vi que te esqueceste do telemóvel. (I saw that you forgot your mobile phone.)
5. Eu vi o cão a correr na rua. (I saw the dog running in the street.)