'For' loop followed by an 'if' statement into 'for' loop

I'm trying to solve a puzzle on hackerrank (the Sherlock and Queries puzzle - http://ift.tt/1uGMdk5). After working on it for a while, I started digging around on the internet for some help. I found one post here http://ift.tt/1C38rdV that confused me. It looks as if he changes this

for (int j = 0; j < N; ++j) {
     if (j % B[i] == 0)
       ...
}

into this

for (int j = B[i] - 1; j < N; j += B[i]) {
     ...
}

Can someone please explain how these two are equivalent?