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

Yes

The word "viajou" is identical in spelling, meaning, and grammatical function in both Brazilian and Continental Portuguese. The only difference lies in pronunciation:

• In Brazilian Portuguese, the vowels are generally more open and the "a" is pronounced clearly [vi.a'ʒo].
• In Continental Portuguese, unstressed vowels are subject to "vowel reduction." This means the "a" becomes much more closed, neutralized, and can almost sound like a swallowed, indistinct sound [vi.ɐ'ʒu].

Brazilian Portuguese Examples:

1. Ele viajou de ônibus para o Rio. (He traveled by bus to Rio.)
2. Meu cachorro viajou comigo. (My dog traveled with me.)
3. Ela viajou de trem para São Paulo. (She traveled by train to São Paulo.)
4. O pessoal viajou no feriado. (The group traveled during the holiday.)
5. O menino viajou de avião. (The boy traveled by plane.)

Continental Portuguese Examples:

1. Ele viajou de autocarro para o Rio. (He traveled by bus to Rio.)
2. O meu cão viajou comigo. (My dog traveled with me.)
3. Ela viajou de comboio para São Paulo. (She traveled by train to São Paulo.)
4. O grupo viajou no feriado. (The group traveled during the holiday.)
5. O rapaz viajou de avião. (The boy traveled by plane.)