There are chemical cleaners that can be purchased at any hardware store that are specifically made to remove paint from hardwood floors. These products can be sprayed on and will break down the paint. After spraying, a good rinse with water will loosen the paint and prepare it for scraping up. They won’t necessarily remove every last particle, so you may need to use something with a bit more bite.
In cases where the initial finishing has rubbed or scraped off, there will be a need for a refinishing job to restore the looks.