The Ansatsuken Fighting Style of Street Fighter practiced by Ryu, Ken Masters, Gouken, Gouki aka Akuma, Sakura Kasugano, Sean Matsuda, and Dan Hibiki is based on Kyokushin Karate, Shotokan Karate, and Shorinji Kempo.
Ryu's Approach to Ansatsuken is a mixture of Kyokushin Karate, Shotokan Karate, and Shorinji Kempo. Not to mention Ryu was inspired by Korean Karateka and Kyokushin Karate founder Choi Yeong-eui aka Masatatsu Oyama (Mas Oyama, Choi Baedal in Korean).
Ken's approach is a mixture of Kyokushin Karate, Shotokan Karate, Taekwondo, Kickboxing, and Taekwondo. Which makes sense since he was inspired by Karate and Kickboxing Legends Joe Lewis and Benny The Jet Urquidez.
Gouki's aka Akuma's approach to Ansatsuken is based on the Aggressive and Hard Style approach and Fighting (Fightin') Techniques of Shorinji Kempo.
Sean Matsuda's approach is based on Ken's mixed with Mixed Martial Arts (MMA) Tatics like Western Wrestling most likely Greco Roman Wrestling. Not to mention his Family's Matsuda Jiu-Jitsu which is based on Brazilian Jiu-Jitsu. Not to mention the Dutch Kicks.
Sakura's Ansatsuken is based on Ryu's but more focused on Speed than Raw Strength and more focused on Kicks than Punches.