Although I can't give you much information, I just want you to know that Hunger Games did NOT give the idea to Battle Royale. Battle Royale was published in 1995 (I think) and Hunger Games was in 2008. I have not read Hunger Games (not planning to) because nothing will ever be as good as Battle Royale.
I have read the book, and just would like to inform you that it is slightly more gory and dark and twisted more than Hunger Games. (Guessing...)
Here is an excerpt from Wikipedia.
"Battle Royale takes place in an alternate timeline—Japan is a member region of a totalitarian state known as the Republic of Greater East Asia (大東亜共和国 Dai Tōa Kyōwakoku). Under the guise of a "study trip", a group of students from Shiroiwa Junior High School (城岩中学校 Shiroiwa Chūgakkō) in the fictional town of Shiroiwa, in Kagawa Prefecture, are gassed on a bus. They awaken in the Okishima Island School on Okishima, an isolated, evacuated island southwest of Shodoshima (modeled after the island of Ogijima). They learn that they have been placed in an event called the Program. Officially a military research project, it is a means of terrorizing the population, of creating such paranoia as to make organized insurgency impossible.
The first Program was held in 1947. According to the rules, fifty third-year high school classes are selected (prior to 1950, forty-seven classes were selected) annually to participate in the Program for research purposes. The students from a single class are isolated and are required to fight the other members of their class to the death. The Program ends when only one student remains, with that student being declared the winner. Their movements are tracked by metal collars, which contain tracking and listening devices; if any student should attempt to escape the Program, or enter declared forbidden zones (which are randomly selected at the hours of 12 and 6, both a.m. and p.m.), a bomb will be detonated in the collar, killing the wearer. If no one dies within 24 hours, there will be no winner and all collars will be detonated simultaneously.
After being briefed about the Program, the students are issued survival packs that include a map, compass, food and water, and a random weapon or other item, which may be anything from a gun to a paper fan."